I’m not going to mention the techniques of bluing up a part as imho these will never change. Or even mention that bluing is an art in its self. This thread will only cover the uses of a hand scraper or not as the case maybe. My method will probably make my old grandfather turn in his grave (he was a scraping hand up until he retired) and the purists cringe into their boots.

A brief explanation about how my alternative method came about.

Trying to keep this as brief as possible; I recently bought a Chinese bench top mill. All in this tread and includes some brief posts on my scraping method (start at page 4 about scraping). http://www.cnczone.com/forums/showthread.php?t=40213
As only to be expected with a Chinese mill it was in need of some serious scraping. So off I set scraping the ways of my machine with my old hand scraper (old file modified) and the usual other tools. It wasn’t until I got to scraping the ways of my column that I stopped to think “there has to be an easier way”. Added to the fact that I had a lot of bearing area to scrape was the fact that there is a 0.09mm (0.00354”) of bow in the column. So I sat and pondered “do I take this somewhere and have it skimmed on a surface grinder or just dig in and do it by hand”. Well the thought of taking it and the price got to me (tight Yorkshire man that I am) so how was I going to remove all that metal without loosing a week of my life. I then thought about the fact I had been using a Dremel type tool to remove some burrs on the castings so I put on a round belt sander type thing (see picture) and proceeded thrashing off metal off either end of my column after a quick blue so I could see where I was removing it. I realised very quickly I was removing metal far quicker and easier than I would have been with my scraper. So I stopped and wondered could this make my scraper obsolete? I went to the bench and picked up my X-Y saddle (already hand scraped) and blued it up on my surface plate. Very nervously to start I removed some of the blue (did a re scrape of the surface) and to cut this story short it worked a treat. Where before I had my surfaces within +/-0.005mm (0.0001968”) of each other I now cannot measure the error as my DTI pointer barely moves while all set up on my surface plate.

The hand scraper is not quite obsolete yet as the sanding bobbin is to large to get right under the dovetails but I have a plan. I remembered seeing some one with a narrow file sander (see here http://www.axminster.co.uk/product.asp?pf_id=21068&name=belt+sander&user_search=1&sfile=1&jump=60 ) and know this will work as a scraper if the front drum is small enough to fit right under the dovetail. If I were doing a lot of this scraping (absolutely no plans to) I would look into modifying (if needed) the nose of the file sander but for a one off job I will probably just stick to my hand scraper to get where the sanding bobbin can not get.

This may all sound like crazy talk to the purists and all I will say is that with the right technique and a little practise IMHO I can do an equivalent job as the above average hand scraper as fast (if not faster), as accurate (if not more accurate) and far easier on the back so don’t knock it until you have tried it. :p

Before anybody decides to take a sander to their ways I would highly recommend a practice on an unimportant part of their casting as it is not as easy as it sounds. It requires a light touch (which varies as the job gets close to finished) and the tool at just the right angle or you will very quickly remove to much metal and spoil your bearing.

Ok guys get the (flame2) out I got my asbestos suit on and what can’t speak can’t lie (that would be my X-Y axes saddle). :D

I’ll post some pictures of my saddle blued up if anyone is interested when I get a minuet?

John

EDIT: Please see post #41 Page 4 before reading the rest of this thread.:) :END EDIT

I had to scrape a set of set precise ballnuts into a set of mounts here at work a few years ago and I used a sanding disc instead of a scraper - primarily due to convenience and time.

In my opinion it is the same priniciple - manually removing small amounts of material to achieve the desired results.

No flames from me....

Scott

If anyone is interested in knowing more about scraping see this thread http://www.cnczone.com/forums/showthread.php?t=11874

John

John,
it sounds good to me. Infact I'll use that procedure when I do my rail risers.

Steve

John, thank you for this post and your description of scraping your mill's ways. Having never done scraping, it has always seemed an almost mystical endeavor. You make it sound much more down-to-earth.

By the way, what's that wooden thing attached to your scraper? :confused: Is it something you add during the conversion from a file?

Best regards,

Randy

like Scotts says, same principal. The other way is file. no one seems to say much about the humble file anymore but they have a tremendous ability to remove material! for roughing, press on the back of the file where you want to remove material - this can provide a lot control

Scraping is a valuable bench skill - anything that isn't flat will be distorted when clamped. So a casting or some precision items should have a reference datum formed by filling & scraping - this is where it comes in as a valuable bench-work skill

The ultimate move into the 20th century is a power scraper. Biax is the on to get, probably come up on ebay, bloody expensive new (are they still made?)

the one thing i can see is that hand scraping tends to have a self regulated depth of cut - when you are finishing with lighter strokes you don't accidentally take out a thou and a half....that might be a weakness of the dremel that deserves some experiment at least

imo its not an art or a guild or anything to be purist about. its a technique that through efforts like yours, more and more will realize is very useful around the shop (for a lot more than machine ways) and that is is not beyond them to get good results from...so i applaud your efforts

Thanks to all that have replied to this thread it is appreciated especially from the experienced members.

I did think that this could have slipped down and off the page never to be seen again without reply. It is only now after my first efforts on my mill that I can really appreciate what my grandfather was trying to tell me nearly 28 yrs ago now. I really wish I had pushed him for more guidance when I had the chance, but such is life. I may at times seem over enthusiastic but now I have seen what can be archived it makes my mind boggle (I can’t get over the flatness of an AA (00) grade surface plate its mind blowing to me, is that sad? lol).

I’ve added some tips I have picked up so far form using my method in case anybody wants to give it a try.

First thing I did was to put the bobbin on the rotary tool without a sanding belt fitted. I switched on the tool and carefully rubbed the bobbin on a piece of sand paper to curve the rubber at the edge (front edge that will contact the metal) so that it would not gouge the metal. Not sure if this made any difference because of the stiffness of the belts.

For roughing I use new belts at what is speed 2 (it has 9 speeds keep it slow) on my tool, as they ware down but before they are completely shot I turn them around to use the other end. Then when both ends are getting quite blunt and clogged I remove it, put it to one side and replace with a new one. If they clog while still good I use the rubber belt cleaning block seen in the picture in the first post to refresh them.

At what I’ll call the middle stage I slow the tool down to its lowest setting and lighten my pressure on the belt. This gives you more control of the amount of material you are removing and helps prevent you taking too much at a time. I’ll keep using the belt, refreshing as necessary until they barely removing any metal and change for a new one at that stage only.

For the finishing stage I reuse all the worn belts, refreshing as I go. Now a very light touch is all that is needed. Never use new belts at this stage it will ruin all your hard work.

Keep the angle of the belt quite low but not so all the width of the belt is used, just the front edge.

To do wider surfaces it will require a narrow rotary tool like pictured, other wise the body will hit the material forcing you to increase the angle of the belt and would give poor results.

Hopefully that will be enough to tell you the basics the rest will only come with practise and experience. I have quickly gained a technique that works very well imo and am happy to work on my mill with confidence. I’m sure that others could do as I did which was to take the plunge and go very carefully to start but I would strongly advise starting on a scrap piece or a part of a casting that will not be used in the final bearings.

I am going to finish my mill using this method and am also going to retouch all the surfaces I scraped with my scraper. I have been considering doing a detailed description with picture of the whole job start to finish but am unsure if there would be enough interest to go to what would be a lot of trouble. If this might interest you please post and let me know. I think it would also be good if the big brains of the zone could asses my methods and point out any problems or just give advice to improve the over all process. I have gained a lot from this site and its generous members it would be nice to give something of value back. Or maybe I should write a book titled “Bringing the Art of Scraping into the 21st Century” and make some money? Nah I don’t think so lol.


John

John, thank you for this post and your description of scraping your mill's ways. Having never done scraping, it has always seemed an almost mystical endeavor. You make it sound much more down-to-earth.

By the way, what's that wooden thing attached to your scraper? :confused: Is it something you add during the conversion from a file?

Best regards,

Randy

Hi Randy,

No problem I just hope it helps others :)

Not quite sure what you are asking; the only wooden thing is the handle of the file.:confused:

John

Mcgyver,

I have read some of the posts (more than once) on the thread I linked to for more information about scraping. You generously supplied a lot of the information so I would like to say a personal thank you to you for that. It was that thread that encouraged me to have a go at the task and the fact I have the camelback straight edge my grandfather gave me.


the one thing i can see is that hand scraping tends to have a self regulated depth of cut - when you are finishing with lighter strokes you don't accidentally take out a thou and a half....that might be a weakness of the dremel that deserves some experiment at least

With this comment in mind and the fact I appreciate your input.

While reading through the thread I came across this statement.


A scraped surface is accurate to a few tenths. (0.0001”) or so.


Just to be sure of what this statement means; is it describing the maximum difference between the highest points and the lowest points on a surface?

To your knowledge is this statement correct?

If not what figure would you use in the statement?

Would that be the best possible accuracy achievable using a hand scraper period?

The best accuracy that could be expected within a reasonable amount of time?

I maybe pushing my luck but would you briefly explain the benefits of scraped bearing on a milling machine. Comparing it to a bearing finished on a surface grinder with a few scrapes using a power scraper (no bluing involved)?

What would be the recommended difference between the high and low points on a milling machines ways (thinking about the oil reservoir effect)?

It may or may not be a big deal (depending on your answers to the figure in question) but I have achieved a higher accuracy on one of the ways of my X-Y saddle using the dremel. I know I could do better but would be unable to measure my results with the DTI I have. I won’t get excited about this until you or another suitable skilled member gives their opinions/answers to my question.

One last point; I’m not looking for bragging rights I am genuinely interested in the skill of scraping and its benefits. I would also be very interested to know if my method is at least equal to if not better than using a hand scraper.

John

I recall being told by an old hand that when finish scraping (ie light, small cuts) the depth of cut typically is in the neighborhood of a tenth, so that may be where it comes from

John thanks for the kind words - but i want to emphasize that old expression "the different between a layperson and expert is 5%". I happily share what i know but you'll get us both into trouble if you take it as being some deep expertise or authority on the matter. I'm no where near qualified to be the scraping expert....in fact by the time you finish the mill i think you're going to get to wear that hat around here :D.

To your surface grinder vs scraping question, don't know if there is a big advantage once the job is done. Some even push back on the value of the oil reservoir benefit. still, its one big honking surface grinder to take the main castings of a mill - if you're not talking production, grinding might be precluded just because the equipment isn't available. I guess the other aspect is the nature of scraping mating parts. A is done to a reference and B is done A. for example, to surface grind dovetails that's going to take some careful work to keep the angles perfect so they mate. when scraping, we don't care, the exact angle doesn't matter, so long as the parts are the same. sort of like making model T's requires standardization and production but for onesy machine reconditioning the hand fit nature of scraping might be more efficient.

I recall being told by an old hand that when finish scraping (ie light, small cuts) the depth of cut typically is in the neighborhood of a tenth, so that may be where it comes from

John thanks for the kind words - but i want to emphasize that old expression "the different between a layperson and expert is 5%". I happily share what i know but you'll get us both into trouble if you take it as being some deep expertise or authority on the matter. I'm no where near qualified to be the scraping expert....in fact by the time you finish the mill i think you're going to get to wear that hat around here :D.

To your surface grinder vs scraping question, don't know if there is a big advantage once the job is done. Some even push back on the value of the oil reservoir benefit. still, its one big honking surface grinder to take the main castings of a mill - if you're not talking production, grinding might be precluded just because the equipment isn't available. I guess the other aspect is the nature of scraping mating parts. A is done to a reference and B is done A. for example, to surface grind dovetails that's going to take some careful work to keep the angles perfect so they mate. when scraping, we don't care, the exact angle doesn't matter, so long as the parts are the same. sort of like making model T's requires standardization and production but for onesy machine reconditioning the hand fit nature of scraping might be more efficient.


I will probably have to buy the book that was mentioned in the other thread. It’s a shame to think out of 50,000 odd members none are skilled in scraping. For the sake of old mills/lathes needing re scraping and diy improvers with these Chinese mills it is a skill that should not be lost and more widely used imho. I’ve spent some time digging around on the net for information but it is thin on the ground to say the least.

Thanks any way for helping me getting started.

As for being an expert, is there any point? One thing for sure even with my very limited knowledge my cheap Chinese mill will be a far better machine for my efforts.

Regards,
John

If anyone reading this has the book (they will know which book I am talking about) it would be excellent if they can chip in here with some information. :)

EDIT :You threw me a bit there with your edit :)

One thing I would like to say about the scraped vs grinded surface. I have tested the effects of “sticktion” between the two and a scraped surface is far superior in eliminating/reducing this effect. END EDIT

I can't believe that guy who didn't know what a file handle was!!!
Does this mean that he has been using files without handles forever?
LOL what is the world coming too?

Also I have a question.
How do you flag the surfaces with a dremmel?

Also I have a question.
How do you flag the surfaces with a dremmel?

Flag?:confused:

I may know what you’re talking about but by another name.

John

Hi Randy,Not quite sure what you are asking; the only wooden thing is the handle of the file.

That was a small joke. Apparently far too small. ;) I rarely use handles on my files, usually holding at the rear of the file body itself.

Best regards,

Randy

Flag?:confused:
Hmm, ...... maybe Flake?
Bob

If we are talking about “flaking” or “spot marks” this can easily be achieved with a flicking action of the dremel. I’ve had a go and achieved good results; with more practice I would think you would not be able to tell the difference between a scraped "spot mark" and a dremel produced one. :)

John

That was a small joke. Apparently far too small. ;) I rarely use handles on my files, usually holding at the rear of the file body itself.

Best regards,

Randy

that, and more so the response, was pretty funny. i don't know how you can stand using files without handles though, and do hope you don't open up a forearm one day!

John, just notice the file scrapper - now i know why you abandon the scraper for dremel - that would be killer using a scraper that short......or did it start out as a 14 bastard and that's how much you had to sharpen it :D try forging one out of a full size file, its a lot easier.

i don't know how you can stand using files without handles though, and do hope you don't open up a forearm one day!

The first stitches I ever received were actually to my left forearm. I was fishmouthing the end of a piece of tubing for a recumbent tricycle I was building, using a half-round file (with a handle!) and the file slipped off the tube, my weight carried my arm forward against the very sharp beveled end of the tubing and I neatly filleted my arm. I could fold back the flap of skin at least an inch. I'm looking at the scar right now...

I find I get much better control in holding the file by the body. Like in draw filing, but I hold files pretty that much now for all filing. Of course, needle files have integral handles, and I use my thumb and first two fingers to control them.

I suppose I am a fairly odd one also in that I mount my hacksaw blades with the teeth facing the handle so I cut on the pull stroke...

Best regards,

Randy

Yeah, at first I thought it might be a designer housing for the electric motor inside it?
But you say that the power just comes from a tendon/muscle/bone type of motor?
How "Fred" (as in Flintsone) is that? :)

Pres

How "Fred" (as in Flintsone) is that?

If files were meant to be used with handles, they'd come with handles! :rainfro:

Best regards,

Randy

John, just notice the file scrapper - now i know why you abandon the scraper for dremel - that would be killer using a scraper that short......or did it start out as a 14 bastard and that's how much you had to sharpen it :D try forging one out of a full size file, its a lot easier.

The scraper you see in the picture started out life with 7” (I read somewhere that 6” was ideal) of blade. You just need to ask Warren aka itsme about these mills as they need a large amount of material removed. I made and am using a new one about 12” long now.:)

John

I have been considering doing a detailed description with picture of the whole job start to finish but am unsure if there would be enough interest to go to what would be a lot of trouble. If this might interest you please post and let me know.

I think that is a great idea!

Steve

question #1 What is flaging?
In the old days when you finished the fitting part of the job, a good millright would "flag" the surfaces. The reason for this was to retain oil on the surface.
It's done by putting the edge of the scraper down on the surface then banging the handle with one hand while turning the scraper with the other hand. The mark left on the surface (if you do it right) looks like a flag blowing in the wind.

question #2
Why do you use file handles?
The first reason is the end of the file is not made for your hand it's made for a file handle. If you use a file on a lathe without a handle you could get hurt real bad if the file kicks back on you. And second I was taught that the oils from your hands made the swarf stick to the file and made it not cut as well as a clean DRY file. Most people think that a file is an abrasive tool, it's not. It's a lot of small cutters in a row and it works better if the swarf falls off.
If you clean your file and flush it with solvent then dry it. the file will cut much better then a oily dirty file.

If you use a file on a lathe without a handle you could get hurt

yup, saw this happen a few times. Each time it was caused by the object thrown by my German high school machine shop teacher when he caught someone filing in the lathe :D

JROM, I agree with you, those newer to the craft (not a trade for me) would do well to learn how to use files. About as important as being able to tap a hole imo

... would do well to learn how to use files. About as important as being able to tap a hole imo

Or better - properly de-burring their parts!

Scott

If you use a file on a lathe without a handle you could get hurt real bad

That is the one situation where I always use a file handle (the only thing I file in the lathe is breaking the edge of a piece I've turned.) And though I'm right-handed, I use the left-hand filing technique so if the file does catch and is flung, I'm not in its path.

Best regards,

Randy

And I thought we were discussing “hand scraping” here?:rolleyes:

question #1 What is flaging?
In the old days when you finished the fitting part of the job, a good millright would "flag" the surfaces. The reason for this was to retain oil on the surface.
It's done by putting the edge of the scraper down on the surface then banging the handle with one hand while turning the scraper with the other hand. The mark left on the surface (if you do it right) looks like a flag blowing in the wind.

So if I told you that “flaging” as you put it or “flaking” as my grandfather put it (a “hand” for over 40 years) is done for show and is actually detrimental to a bearing way, you would already know that?

John

I like my version better. I've seen alot of high end machines over the years with "flaged" ways and I don't think they went to all that trouble for show.
Also when you use abrasives on soft metal some of the rocks always get embeded in the metal........not to good for a bearing surface. Except for surface grinders grinding hard material.

I like my version better. I've seen alot of high end machines over the years with "flaged" ways and I don't think they went to all that trouble for show.


I’ve just been Googling and found this. http://www.desktopcnc.com/swarf/frosting.htm Seems to confirm what my grandfather told me.


Also when you use abrasives on soft metal some of the rocks always get embeded in the metal........not to good for a bearing surface. Except for surface grinders grinding hard material.

So how do they stop grains from a grind wheel from embedding into ways finished on a surface grinder "cast iron" which are not a “hard” metal?

John

And I thought we were discussing “hand scraping” here?

My apologies, John, for diverting your thread.

So if I told you that “flaging” as you put it or “flaking” as my grandfather put it (a “hand” for over 40 years) is done for show and is actually detrimental to a bearing way, you would already know that?

Please explain further, John. From what I have read on scraping, the flaking creates mini lubricant pockets to avoid the moving part wringing onto the stationary part of the bearing. Is that wrong, or is there something in the flaking process that disturbs the surrounding surface?

EDIT: You must have posted the immediately preceeding entry while I was composing this one. I withdraw the question. :o

Best regards,

Randy

....would do well to learn how to use files. About as important as being able to tap a hole imo

Oh come on: tapping holes is nowhere near as boring as filing :) . Somehow as an apprentice I successfully avoided ever having to do the filing thing to make a square peg and hole that would not allow a 0.001" feeler gauage in the gap. And I still hate filing or scraping.

EDIT: I guess I have to apologise for diverting your thread. And also commit the sin of saying I think your Grandpapa was wrong; at least based on what I was taught. The nice mottled flaking is done in a nice symmetric pattern for visual effect but the underlying purpose is to provide lubricant reservoirs.

My apologies, John, for diverting your thread.


No need for an apology :D I was jesting.

John

EDIT: I guess I have to apologise for diverting your thread. And also commit the sin of saying I think your Grandpapa was wrong; at least based on what I was taught. The nice mottled flaking is done in a nice symmetric pattern for visual effect but the underlying purpose is to provide lubricant reservoirs.

I think it would be wise for me just to leave this thread to you guys:) .:wave:

John

Well John, I tried your method today. Works excellent.
Very very fast once you get the hang of it. Very light touch as you say. There is no muscle work whatsoever using a grinder.:D
I held the dremel with a very very light feel. I pretty much just held at it's center point in my hand so it would remain level. Then just lightly touched down to the hi spots with no hand pressure at all once the parts were getting close.
It is quite different than hand scraping that is for sure and I can see where somebody with a shaky hand could get into trouble fast. But I found it very easy after an hour or so of practicing.
These are not bearing surfaces so they just needed to be nice and flat.
I'll post 4 pics and explain them.

Pic1 is the top of the headstock riser block that the head stock mates to, which I had made flat to the surface plate.

Pic2 is a before shot of the headstock that sits atop the headstock riser- So the head stock would be made flat using the head stock riser block top surface as the reference.


Pic 3 is the head stock surface after using the dremel for about an hour referencing it to the headstock riser surface.

Pic4 was a final test and it is very interesting to note. This is the surface of the head stock AFTER being made flat to it's reference surface the head stock riser. I placed the head stock on the surface plate this time and note the pattern is now reversed. The high spots are exactly where the areas were never touched with the dremel.
Very very effective method using a dremel IMHO if you can handle the very light touch that is needed to make it work.
http://i109.photobucket.com/albums/n48/S_J_H/cnc%20bench%20lathe/cnclathe020.jpg
http://i109.photobucket.com/albums/n48/S_J_H/cnc%20bench%20lathe/cnclathe021.jpg
http://i109.photobucket.com/albums/n48/S_J_H/cnc%20bench%20lathe/cnclathe023.jpg
http://i109.photobucket.com/albums/n48/S_J_H/cnc%20bench%20lathe/cnclathe022.jpg
Steve

Also when you use abrasives on soft metal some of the rocks always get embeded in the metal........not to good for a bearing surface. Except for surface grinders grinding hard material.

Just a quick note on this comment; because I am willing to learn and question what I believe to know I took a microscope to my way surfaces. Not the most high tech gear but good enough IMVHO to check JROM’s point. At fifty times magnification there was no sign of embedded grit from the abrasive belts. I put this down to the fact that they are very well adhered and the very low cutting force. Because of the high contrast between the two materials it would have been easy to see unless they are so microscopic and I really needed a probing electron micro scope which I have sent away for an overhaul so was unavailable :D

Well John, I tried your method today. Works excellent.
Very very fast once you get the hang of it. Very light touch as you say. There is no muscle work whatsoever using a grinder.:D
I held the dremel with a very very light feel. I pretty much just held at it's center point in my hand so it would remain level. Then just lightly touched down to the hi spots with no hand pressure at all once the parts were getting close.
It is quite different than hand scraping that is for sure and I can see where somebody with a shaky hand could get into trouble fast. But I found it very easy after an hour or so of practicing.


Hi Steve,

Please to here it went well.:) Thanks for posting.

Did you use an abrasive belt on a rubber bobbin or a grind wheel?

I use the former and do know there are at least two different grit grades (could be more?). If you are using the same and are finding that you are needed too light a pressure to control the removal rate you could use an already partly used belt or give it a quick spin on something like concrete to blunt it a bit. Obviously by the sounds of things this is not a problem for you but would help anyone else who is a bit heavy handed.

John

John, I used those tiny little abrasive bands on the rubber bobbin. I also removed the small outboard steel washer on the rubber bobbin and this gives a little smoother action.120 grit works pretty good for fast removal.
I did my rail risers today on the lathe bed. All I can say is this method will very quickly get you a nice flat surface. One thing though, sure is messy!

Fellow citizens, the thread is "Bringing the art of scraping into the 21st century", and no way will I comment on the use of an angle grinder or other abrasive method to ensure accurate fits in machinery.

The next thing someone will advocate using a sheet of wet & dry paper on a paving stone to lap a machine part flat.

Dear John, go back to bed, read a good book, but don't propose bodge methods as a synonym for skilled work practice for the 21st cent.

Anybody who grinds cast iron is asking for trouble.
Cast Iron in it's natural state is machined and scraped, but when it's flame hardened it can only be ground.

One last thing on bluing a surface plate, if the blue transfers to the part being tested and shows up as blue it's TOO thick and just smears everywhere, it should be applied sparingly and when transferred should show up as a GREY marking on the part.
The final test for an accurate surface is 25 dots of contact per sq inch.
Ian.

Ian,
You probably can't control the rotary tool with as much precision as a skilled hand scraper and it is certainly limited in use for surface type( dovetails would be very difficult to use it on) but for a hobby level work you can still beat the heck out of the machined finish done with one of our hobby mills. I'll estimate flatness to well under .0003" no problem and done very quickly. You can dust off a very small amount of material with the right touch.
In my case I am only flattening clamping surfaces not a bearing surface.
The surface is very good now.
I'll have to get a .0001 indicator and test out just how much control I can get in material removal with the rotary tool.
In my pics I deliberately used a heavy coat of hi spot blue just for the pics. In reality my flats show only small speckles that are very difficult to see.
Steve

handlewanker,

I could sit here and type quite a few word is response to your post but I will not. I certainly will not insult you with a comment like “Dear John, go back to bed, read a good book, but don't propose bodge methods as a synonym for skilled work practice for the 21st cent”. At the end of the day I can not respect the opinion of a person who is not at least willing to entertain the fact that there could just be another way of doing things. I could say “give it a try and see for your self” but I know for a fact you would not. All I will say is “what can’t speak can not lie” and ask you is the world flat or round?

Regards,
John

At this point I could go into detail describing the accuracy I have archived with my method (burn him, burn him lol) but will just say “try it for yourself, get a piece of scrap and give it a try then judge for yourself”. It will require practice and some experience to achieve good results but that has to be expected. Or if you read through this thread and decide it’s not worth trying and cannot possibly achieve good results because other members say so then move on and good day to you.

This will very likely be my last post in this thread unless some one has a genuine question or an opinion that they are at least willing to discuss in a civil manner. I have nothing to prove here all I was trying to do was help others. The fact that one member gave it a try and was happy with his results has made all my posts in this thread worth it. :)

John

Because I have never been one to go quietly and I have mentioned on more than one occasion “what can’t speak can’t lie” I thought I would put some money where my mouth is and add some pictures of my saddle. Not quite perfect but I am still perfecting the technique.

All the work on this has been done with a rotary tool.
For the sake of the pictures I added more Prussian blue pure dry pigment and thinners so I could get a very thin coat on the inspection grade surface plate. The saddle was slid approximately 6mm (1/4”) vertically and horizontally with no down pressure and the pictures were taken in day light with no flash. There is a little glare from the sun which was quite low at 6.00 p.m.

When I have perfected the technique I will post updates if needed but the 9000 rpm of my rotary tool is to fast and about 1000-2000 rpm is better. The bobbin is approximately 15mm in diameter and I have switched from the standard wood sanding belts to wet and dry belts ranging between 250- 600 grit used dry.

John

EDIT: I have added a picture of the saddle before scraping. :)

I'll have to get a .0001 indicator and test out just how much control I can get in material removal with the rotary tool.


Steve,

The 0.0001” would not be enough try 0.00005” or less.:)

John

Hallo John, as the title of the thread is referring to SCRAPING, which I might remind you is a precise surfacing process, I will agree that you CAN produce a surface to your own satisfaction by any method you choose, but I still consider grinding it bodge work where machinery refitting is concerned, especially on sliding surfaces.
Sorry if it ruffles your feathers, but that is my opinion.

I will further add that I HAVE had the occasion to use a 100mm angle grinder on my lathe to prepare a flat surface so that I could mount a steel plate carrying the flat pulley drive mechanism behind the headstock.

The lathe originally had an overhead belt drive from line shafting, but got bombed during the war, and laid in the corner of a factory covered in rubble for a number of years.

I used the angle grinder because the surface had a thick scale from the casting process, and it was required to get down to bare metal so that the mounting plate for the belt drive mechanism could be fitted on a flat surface.

In no way would I consider it a parallel to the scraping process, but served to produce a flat surface for static mounting.
At the same time the surface was tested by chalking it and mating the mounting plate,(previously flattened), in the same way you would use a surface plate.

The final test was a dab of blue on the plate to make sure that there was enough surface area in contact to give a stable bolting face.
The end justifies the means.

If you're happy with your method, use it, but don't describe it as bringing the ART of scraping into the 21st cent, it's just another way to get to where you want to go.
I'm sure there will be many people that will use the method, so enough said, on with the motly.

By the way, are you a member of the flat earth society? Just asking as you did mention it.LOL.
Ian.

Hallo John, as the title of the thread is referring to SCRAPING, which I might remind you is a precise surfacing process, I will agree that you CAN produce a surface to your own satisfaction by any method you choose, but I still consider grinding it bodge work where machinery refitting is concerned, especially on sliding surfaces.
Sorry if it ruffles your feathers, but that is my opinion.
.

It is not your opinion that ruffled my feathers as you put it but the wording of your reply. Leaving all the niceties a side if we can? I am willing to listen to other peoples opinions we all have the right to that I presume?

Please educate me to why in your opinion the method I describe here is a bodge method. Is there a problem using “wet and dry” paper on cast iron bearing surfaces keeping in mind that the cutting forces are extremely light?
If another method can produce a surface at least as good as a scraped surface can that be classed as a bodged method?

For some unknown reason that I don’t know handlewanker has left without reply. Maybe he will return later and answer my question if not for my education then for the benefit of anyone else reading this thread.

I am not arrogant enough to say there are no issue using the method I have described and am very willing to be educated as that is the main reason for me joining this website. So if anybody more educated than me would like to step in and give some answers to the above questions PLEASE do. I would not want anyone to use this method if there is a problem. I started this thread with no other aim but to help others as I have been helped.
One thing I have learned from this thread is that trying to help others is a thankless task and should be avoided in the future.

At the end of the day it is the reader’s choice to ether use the information or not but it has been given in good faith.

I will admit that while writing the first post to this thread I did consider adding a question mark at the end of the title but being human which I am, forgot.

At this point I would very much appreciate a moderator deleting this thread if that is at all possible.

John

EDIT: I’ve just learnt that you can edit the title to a thread :D

One thing I have learned from this thread is that trying to help others is a thankless task and should be avoided in the future.



I read through this before I started to reply, and actualy did see a few thank you's thrown in. ;) I'm sure plenty of others have gotten some useful info from this as well. We try to never delete threads here unless they get completely out of hand. 1500 views and one person doesn't likethe terminology you used. Ignore it and move on.

Sorry,I know little on scraping.Would not Moglice bring the art of scraping into the 21st century?I have read Molgice does not require scraping.I don't think so,as 100% contact would not allow for lubricant.Should Moglice be scraped or spotted?
Larry

For some unknown reason that I don’t know handlewanker has left without reply. Maybe he will return later and answer my question if not for my education then for the benefit of anyone else reading this thread.

I am not arrogant enough to say there are no issue using the method I have described and am very willing to be educated as that is the main reason for me joining this website. So if anybody more educated than me would like to step in and give some answers to the above questions PLEASE do. I would not want anyone to use this method if there is a problem. I started this thread with no other aim but to help others as I have been helped.
One thing I have learned from this thread is that trying to help others is a thankless task and should be avoided in the future.

At the end of the day it is the reader’s choice to ether use the information or not but it has been given in good faith.

I will admit that while writing the first post to this thread I did consider adding a question mark at the end of the title but being human which I am, forgot.

At this point I would very much appreciate a moderator deleting this thread if that is at all possible.

John

EDIT: I’ve just learnt that you can edit the title to a thread :D

John;

Here you have another bunch of THANKS!. I haven't posted before on this thread, but I was following it. Please, don't delete it.

Regards,

Kreutz.

For some unknown reason that I don’t know handlewanker has left without reply. Maybe he will return later and answer my question if not for my education then for the benefit of anyone else reading this thread.

I am not arrogant enough.....

Give yourself another 26 years and then maybe you will be the cantankerous old codger even if you are in the wrong hemisphere.

And I am not going to apologise for being off-topic, sometimes a bit of levity is needed.

Once more to the breach dear friend, once more, so, John, I finally went to bed, it was after 4.00AM our time, having turned into a pumpkin.
I'm sorry if I left you panting for a reply, but I know that in the true spirit of forgetfullness, I will try to clarify what I'm so dead against that perturbs you.

Firstly, when you have an existing slide, male or female, dovetail or square section, you must first make the male half true to the original surface configurations, I.E. a lathe bed should be level and straight by any means you can devise, whether it be with an angle grinder, planer, or surface grinder, and a mill base casting must have the various slide ways, be it a turret mill with dovetails in the bed or a horizontal with vertical vees, made true before the saddle can be applied to it.

The surface is now carefully and evenly scraped all over to remove the gouge marks left by the previous methods, and this includes surface grinding.
If you examine the surface under a 50 X magnifier you will see that it is like a ploughed field, granted very evenly ploughed but nevertheless having peaks of crumbly material that will by no stretch of the imagination support another surface of like finish.

The result, if you think a surface ground finish is good enough, is that the peaks will rapidly wear down and the resulting residue becomes gritty grinding paste that further gouges the surface and accelerates wear.

All of this wear down, or as some daft idiot once told me, "it's the bedding down you have to have", occurs where the slides work on one another, and in the case of the lathe bed the bed ways, will rapidly become untrue just where you use it the most, at the chuck end.

The scraper has a flat scraping motion, cutting on a fairly broad front, even though the front is a curved shape, and one of the reasons you should not raise the handle end above 30 degrees to get the scraper to cut is because you will just dig furrows instead of levelling the surface.
The curved front is important otherwise you'd dig in the corners of the scraper and make it impossible to attack small areas or high spots, don't believe me, try it for yourself.

The raising of the handle to get it to cut, indicates that it's high time to resharpen the scraper, otherwise you just rub a hard skin on cast iron, especially as it's a material that work hardens beautifully.

When using the scraper you should work at 45 degrees to the forward movement, alternatively changing direction, and criss crossing your path, so that you don't dig yourself into a hole.

The surface should have a series of overlapping basket weave like patterns as you proceed, and by this manner you will bring even the most worn surface dead true, as good as a professional would get.

I cite you a case history in brief.
The lathe I aquired, a Colchester Bantam circa 1920/30, had, and I kid thee not, .013" of wear on the raised vees from the chuck to halfway along the bed.

A candidate for a regrind by some expensive engineering works no doubt, for there is no way that even the great Jehovah himself would contemplate scraping that much material off of the other unworn end, let alone one of his relapsed sinners.

So I hand planed the three raised vees and two flats with a hand planer device, which is another story, so I won't bore you, and finished off the "ploughed field effect" by a scrape all over.
Needless to say the saddle, when first laid on the bed,had daylight under it, and you could see light under it viewed end to end, but by carefull attention to keeping the crosslide ways square to the longtitudinal axis a good fit was attained, and now as a testimony for the work involved I can bore a hole 50mm diam and 100mm deep without being tapered.

I've seen some people put up with .002" taper on a 6" length by filing the outside diams of work pieces, but when you've got a taperd bore it's enough to drive you to drink.

So John, I dinna like the hand grinding of a slide way, but if it suits your taste and you're happy with the end product, go for it, but don't promote the assumption that it is the next logical step forward or an evolutionary step in "the art of scraping", for by so doing I would be deeply affronted.

I would however add that it would be an admirable alternative for producing surfaces that don't move but need to be flat or otherwise, and I frequently use an angle grinder on steel structures when bolting faces are required.
Ian.

'Lo John, I see you mentioned that you were having trouble with a too fast hand grinder.
I take it that's one of the electric die grinder types with all the sanding and grinding thingies you get in a kit?

If it's a mains 240 volt plug in type, you can use a dimmer switch, which will handle about 350watt, to control the speed, but if it's a rechargeable one with built in batteries you're stuck with it.

I would have thought that a higher speed would have been beneficial otherwise you just rub the surface and load the stones up.
You mentioned that 1000 to 2000 rpm would be OK, so why not get a flexible shaft (on Ebay) and run it off of a 1/8th hp motor, they do about 1425 rpm or 2800 rpm usually.

My 13mm electric drill does 2400 rpm top wack, and has a variable speed trigger.
Ian.

'Lo John, I see you mentioned that you were having trouble with a too fast hand grinder.
I take it that's one of the electric die grinder types with all the sanding and grinding thingies you get in a kit?.

http://www.cnczone.com/forums/showthread.php?t=43426

And I do appreciate the information regarding scraping btw.

And I am not going to apologise for being off-topic, sometimes a bit of levity is needed.

No need for an apology :D I was jesting.

John #33 :rolleyes:

John;

Here you have another bunch of THANKS!

Thank you :)

John

I have been following this thread but maybe I missed something.
30 or 40 years ago I seem to recall that the quality of scraping was measured by the number of points to the square inch and not by a perfectly flat surface. Different surfaces depended on load factors and application, required a different number of points,A tradesman I worked with took a lot of pride in the different effects created by scraping he produced.
WJF

I have been following this thread but maybe I missed something.
30 or 40 years ago I seem to recall that the quality of scraping was measured by the number of points to the square inch and not by a perfectly flat surface. Different surfaces depended on load factors and application, required a different number of points,A tradesman I worked with took a lot of pride in the different effects created by scraping he produced.
WJF

Hi WJF,

Welcome aboard and thank you for adding the information, I as I am sure many others would be grateful if you could add any detail to the point you made; for the sake of education.

I’m not looking for bragging rights I am genuinely interested in the skill of scraping and its benefits. Post #9 page 1.

On the subject of points contact I have added a pictures taken in the same circumstances as my last posted pictures post #41 page 4. I have also included a close up picture of the surface with out blue. I have only had about 10 hrs total practice but see no problem using the method as described in the same post as the aforementioned pictures producing a surface with 25, 50 or 100 points contact. http://www.cnczone.com/forums/showpost.php?p=341540&postcount=41

As handlewanker has already said he see no problem using the method for none sliding surfaces BUT the method used for sliding surfaces would be a “bodge” method in his opinion. What I would like to determine as a FACT would be if it is indeed a “bodge” method for sliding surfaces? I would be grateful and happy to concede that my method is indeed detrimental to a sliding surface if this is indeed a fact. I’m using it on my own mill :eek:

I don’t know how useful the added pictures will be but they maybe enough to show why it is a “bodge” method?

EDIT:Just for the sake of onlookers the difference between the blue points and the surrounding surface is less than 0.00005” (0.00127 mm).

John

.... no problem using the method for none sliding surfaces BUT the method used for sliding surfaces would be a “bodge” method in his opinion. What I would like to determine as a FACT would be if it is indeed a “bodge” method for sliding surfaces?...John

I do not see why it should be considered a bodge method or why it is not suitable for sliding surfaces. Analyse what is going on with scraping and what type of surface is being generated.

Using a scraper generates a scalloped surface from the curved cutting edge of the scraper. Using a rotating abrasive tool will generate a scalloped surface from the periphery of the tool.

Flat is measured only on the high spots, the peaks between adjacent scallops, and as wjfiles points out the number of peaks, spots of blue, per square inch is an index of the quality of scraping. For a highly loaded sliding surface a high peak density is needed for a static mounting surface a low density will suffice.

Provided the same spot density has been obtained by either method I do not see how they would perform differently in the same application. If someone wants to argue differently I would like to see their reasoning not just a blanket 'it is the wrong technique'.

If someone wants to argue differently I would like to see their reasoning not just a blanket 'it is the wrong technique'.

That is ALL I am asking for.:)

Geof,

Thank you for your post it is VERY much appreciated if only to stop me thinking I am talking complete ****e. I am also still happy to be corrected for my ignorance if indeed I need to be?

John

Sorry,I know little on scraping.Would not Moglice bring the art of scraping into the 21st century?I have read Molgice does not require scraping.I don't think so,as 100% contact would not allow for lubricant.Should Moglice be scraped or spotted?
Larry

Hi Larry,

I’ll be the first to admit I know virtually nothing about Moglice but it is something on my list to investigate in the near future. Hopefully some one in the know will answer your question and it will get me started in the subject.:)

John

EDIT:See here fourth paragraph form the end.http://www.moglice.com/newsite/frames/straightframe.html

Analyse what is going on with scraping and what type of surface is being generated.

Using a scraper generates a scalloped surface from the curved cutting edge of the scraper. Using a rotating abrasive tool will generate a scalloped surface from the periphery of the tool.

Just a note on this point; when removing a blue spot with the tool I use I don’t drop it on to the blue and then lift off. I do a kind of flicking action vertically over the surface so the worked point will be close to flat.

I don’t think the shape is what is important to the suitability of my method for sliding surfaces. I think it is more down to what effect using “wet and dry” paper has on the surface.


The surface is now carefully and evenly scraped all over to remove the gouge marks left by the previous methods, and this includes surface grinding.
If you examine the surface under a 50 X magnifier you will see that it is like a ploughed field, granted very evenly ploughed but nevertheless having peaks of crumbly material that will by no stretch of the imagination support another surface of like finish.

This statement interests me and so the question is does using “wet and dry” paper leave an unsuitable surface as described here where a surface finished with a hand scraper does not?



John

Ok iv'e been lurking for a while and have said my hello's on another thread so now time to get stuck in.

Scraping has two functions.

1 Allow for oil pockets on a very smooth surface IE Ground surface or cylindrical so that parts will not wring together.

A surface ground finish under a 50X lupe it might look like a ploughed field but a scraped source under the same lupe would look like the Himalayas

2 To mate one surface with another neither of which might need to be flat

I bought a surface grinder on Ebay, Jones & Shipman 540 and like all machine of a certain age "The Motor Said Made In 1951" it had wear on the cross slide ways.

Using said grinder i ground some 1 1/4" square bars dead flat and used them to get a datum on the ways there was so much to come off i used an angle grinder:eek: using a a flexible backing pad i got the ways to pretty flat them hand scraped them to perfect then i used that part of the machine to mate to the other part of the machine.

Having been a toolmaker for some years past i can say that the machine is as good as any i used in my working life i have even used a brand new one.

So what is the problem ?

Phil_H

P.S. I have also got a Biax scraper now:wave: and will be doing a job on my Bridgeport I may take pics along the way to show here.

Ok iv'e been lurking for a while and have said my hello's on another thread so now time to get stuck in.

Scraping has two functions.

1 Allow for oil pockets on a very smooth surface IE Ground surface or cylindrical so that parts will not wring together.

A surface ground finish under a 50X lupe it might look like a ploughed field but a scraped source under the same lupe would look like the Himalayas

2 To mate one surface with another neither of which might need to be flat

I bought a surface grinder on Ebay, Jones & Shipman 540 and like all machine of a certain age "The Motor Said Made In 1951" it had wear on the cross slide ways.

Using said grinder i ground some 1 1/4" square bars dead flat and used them to get a datum on the ways there was so much to come off i used an angle grinder:eek: using a a flexible backing pad i got the ways to pretty flat them hand scraped them to perfect then i used that part of the machine to mate to the other part of the machine.

Having been a toolmaker for some years past i can say that the machine is as good as any i used in my working life i have even used a brand new one.

So what is the problem ?

Phil_H

P.S. I have also got a Biax scraper now:wave: and will be doing a job on my Bridgeport I may take pics along the way to show here.


Hi Phil_H,

Do you have an opinion on the question I asked in the previous post?

Would very much like to see pictures of your scraping if you could be so kind as I have never seen I scraped surface close up other than that on my camelback which may be different from that on a sliding surface.

John

Hi John.

Sorry no pics. But i would have thought using wet N dry would be most suitable for removing high spots on a shaft say.

But hey whatever works for you.

Phil_H

P.S. I have also got a Biax scraper now:wave: and will be doing a job on my Bridgeport I may take pics along the way to show here.

Would like to see these pictures.:)

But i would have thought using wet N dry would be most suitable for removing high spots on a shaft say.

So are you saying wet N dry for a shaft yes but for a mills ways no? Sorry to be pushy but I just want closure on this thread if I can.:tired:

John

Hi John,

So are you saying wet N dry for a shaft yes but for a mills ways no? Sorry to be pushy but I just want closure on this thread if I can.

No whatever works for you. But you would of course clean all surfaces before assembly. That goes for any method.

Phil_H

Hi John,

No whatever works for you. But you would of course clean all surfaces before assembly. That goes for any method.

Phil_H

Thanks Phil your opinion is very much appreciated :cheers:

John

Hi John, sigh, once again I will state, not out of wanting to be awkward but just to produce the end product as is required, that if you use ANY ABRASIVE method you will by the nature of the abrasive material make a ploughed field, (multiple vee grooves) of the surface and this will leave you with millions of sharp pointed crumbly peaks that under the sliding of one piece of metal on another just shear off and so you end up with a rapidly lower, although miniscule, area of non support.

Abrasives will produce grooves and sharp jagged peaks, whereas scraping will result in a series of undulating hills, more condusive to oil film retention and load bearing.

The effect is exacerabated by the now grinding grit like metal particals that during the "break in" period make the oil black and this is the top surface of the slide grinding itself down to a level that will allow oil to remain between the two faces.

Some will say that this is normal bedding in, but not if the surface has been removed in it's effort to level it, and very much more apparent where the slides work constantly.

The scraping process is the levelling and smoothing of the top layer, and one side effect, although this is not to be encouraged but has been proposed by some brave fools as a method to produce longevity in sliding surfaces, and that is to allow the scraper to cut BLUNT for the last overall scrape, (rub?), so that the surface becomes workhardened and has a hard skin.

I will not comment on this, as it has logic but is not supported by clear field test results, and most machine fitters I have spoken to just shake their heads and give you a long withering look.

Once more for the record, you can grind for static surface preperation, but sliding ways need a different approach.
The scraping process is not hard to achieve and once you gain control of the process you never forget it.
It's easier and less tiresome than filing.

If you want a filing exercise, take a 2" square block of steel and by hacksaw and file make it into a hexagon with 8 sides, (6 sidesand 2 end faces), true and square in all aspects and to size within .02mm (.001") etc.
This makes a good talking point and display piece, and sets you apart from the general scruff.

Over a period of time two surfaces will lap themselves to a very smooth finish and have a very large bearing area, and it is only the presence of the oil film that prevents them from making contact.

Incidently, on the subject of surface areas and supportive oil films, if you take a cars big end bearing as a case study you will observe that the crank pin surface is ground, and the whitemetal shell is bored.
Both work together without destroying one another due to the oil film that is applied at a pressure of about 50 to 80 lb psi.

If any bearing could be described as being less suitable for longevity then you would have to say a soft lead like metal on a steel surface would be the last to use, so why not on a lathe or mill slide way?
The answer is the oil film that is pumped at pressure and so like an air bearing keeps the two surfaces apart.

The design of the engine, with big ends enclosed, lend themselves to having pressurised oil applied liberally to be recovered and reused over and over again, whereas the lathe/mill slides only have oil present on the surfaces of the slides, if and when the operator decides to apply it, and then it's not at pressure.

BTW, a 50 X magnifier is a microscope not a loupe, and a groove .001" wide is like looking at a screw thread with a 20 tpi pitch.
Ian.

Last word before I go out for lunch, I suppose someone will suggest that Brasso could be added to the lube oil to get the slide ways to gradually bed themselves in without the effort of stripping the machine down to do the job the proper way.( last seen being carried off kicking and screaming incoherently in a foreign tongue, in a tight fitting jacket)
I.

Ian,

First of all you will be relived to know that I have changed the title of this thread from a statement to a question. This does not imply that I am still questioning your opinion but implies that the subject has been/is questioned. I would also like you to know I have read every word of your posts, well at least what did not include condescending or personal remarks. I would also like you to note that even though others were implying that my method might be without fault I did not rest on my laurels there, I did in fact still question my technique.

I understand completely your description of the effect on a surface at a microscopic level. Question do come to mind about this but I do see how it would/could become a self perpetuating process of almost a lapping scenario (I used lapping to give the idea of what would be happening and know it is not true lapping in the real sense of the word).

So where is my thinking now and a little explanation of why I have looked for another method? In a ideal world the mill I bought (knowing what I know now it would have probably been a better idea to buy an old mill and restore) would have been dismantled and re machined to bring all relevant surfaces up to at least a standard that would need very little scraping. The cost of doing this would have been ridicules for a hobby standard milling machine. So a relatively quick alternative method was looked for hence the use of a grinding tool, initially to reduce the surface so only a reasonable amount of hand scraping would be required. Because of the surprising amount of control and the ability to remove such a small amount of metal accurately I questioned the fact that I would need to use a scraper at all. If I had given you the X-Y saddle of the mill in its delivered condition you would have despaired imo. It was twisted and the surfaces where far from parallel some people would be happy to use the machine in this condition but I was not. Using the hand grinder it now has no twist and the surfaces are accurate to the extreme (far more than was necessary but became a study of the scraping technique). To use hand scraping alone would have been ludicrous so IMVHO I believe my method has great merit in these circumstances. Having read your posts and now fully understanding the merits of the hand scraped finish I will add one more process to my methods. That will be to hand SCRAPE the surface when the surface is near completion to attain the required surface effect. For a none sliding surface this extra process will be omitted.

My understand now is that I would agree (unless someone else has an opinion of what goes on at the microscopic level in this scenario and can explain why a grinded surface finish would be acceptable for a sliding surface) that a grinded surface would in fact be a “bodge” (I would have used the word “unacceptable”) method.

I would like to thank you for your fortitude in this discussion as without it I would be misguided and using bad practice which is not what I would want. Just in the future please be a little more patient with me/us uneducated types and spend a little time educating instead of making us/me feel inadequate and belittled. If you had used your “go to bed…..” statement to my face I would have punched you in the nose.:)

Regards,
John

Hi John, any method that attempts to sidestep the correct way to achieve the accepted end result is a "bodge" method, as opposed to an alternative method, which broadly speaking means that you should not expect a brain surgeon to take you seriously if you suggested using a tin opener for the opening procedure, even though the end result is the same.

My beef is that the thread title is highly suggestive and tantamount to a means for updating an antiquated method of machine restoration and modernising it for 21st cent needs.

Needless to say that if you are happy using your method, I would not stand in the way of "progress" by categorically stating that it should not be performed as you instruct so clearly, but I will stand my ground if there was even the slightest suggestion that the scraping method was being "modernised", supplanted, used in preference to, instead of as an alternative, although questionable, way to get home.

At the end of the day, any method, however unorthodox, will dictates how you, with the knowledge and means available to you, will achieve your ambition, be it DIY brain surgery or machine tool rebuilding, and I would defend your rights as to the choice of methods, to the last pennoth of my pension.

On the subject of old machinery restoration, if you haven't got the necessary equipment or knowledge to do the job as laid down, then you will be walking around blindly in no mans land, which doesn't mean you can't do it, just that the end results don't always come out as you desire, even though the wheels appear to go round and round smoothly.

Missaligned slides are difficult to detect and always lead to errors when testing the final result.
A typical example is the refitting of a lathe saddle to the longtitudenal ways without a thought for the crosslide allignment.

It's true what you say about the remachining by an outside source to initially restore slideway allignment prior to finishing, due to the cost of labour, but sometimes it's the only way to go.

The long way, if time is of no importance, is to have a reference surface plate of sorts to reveal the worn areas, and then hack into the offending metal with a hammer and chisel, angle grinder, file or wet and dry round a piece of wood, it doesn't matter as long as you end up with alligned ways for final finishing.

The irony of it is, the metal to be removed is the metal that is not worn, and is probably the original surface of the machine slide when it was new, still bearing the scrape marks of the craftsmen when it was made.

For anyone who's intrested in hand lathe bed restoration for little cost and has the time to spare, I'll attach a photo of a lathe bed hand planer tool I made to restore a lathe bed that was badly worn near the chuck end, the usual wear area.
Ian.

Interesting reading. No real knowledge of scraping, just some thoughts.

Handlewanker had mentioned planing a surface prior to scraping. Oldmanandhistoy's method seems to fall somewhere between it and scraping, or perhaps an alternative to planing?

I think the objection to finishing a sliding surface largely depends on the actual surface finish the grinder leaves, and would think that 600 grit would be a minimum for finishing. Perhaps the idea of finishing with a dull scraper to work the groves from grinding flat. More by forming then by cutting.

Dale

you should be careful with this tern. remember
x is the unknown
spert is a drip under pressure
expert = unknown drip under pressure
Dar

Hi, a dull scraper was someone's suggested method, but not practical.
If you hit cast iron with a dull scraper you work harden the surface and then it makes any correction very difficult.

Nothing takes the edge off of a scraper better than work hardened cast iron, and for this a carbide scraper is the worst culprit, making an inexperianced user more prone to forcing the scraper to cut when in actual fact the surface is resisting by generating a hard skin, that is unless you're taking paint off a galvanised steel sheet with one, seen that done.

If you put two freshly ground iron surfaces together and have a film of oil between them, then they will not wear in a million years, provided the oil film is maintained.
The moment the two faces slide one on the other the oil migrates out of the gap and so the faces get closer until metal to metal contact occurs and pretty soon they just eat into each other.

The perfect bearing arrangement would be two mirror finished surfaces sliding on an oil film maintaind by pressure feeding oil between them, as in an engines big end bearing with steel on white metal, and high oil pressure feed.

Unfortunately it is impractical to have pressure fed bearings on machinery due to the contamination by the mixing of lube oil and coolant that would occur, unless some means were taken to contain the lube and recirculate it.

The purpose of having two dissimilar metals for bearing materials is so that one of them becomes a sacrificial part and is easily replaced.
A steel crankshaft and whitemetal bearings are typical examples.

Furthermore, the grinder has not been made that can grind a perfect slide way, due to wheel wear, wear and tear on the machine itself and slideway clearancs that vary as the pressure of the work load comes on the work being ground, and in addition to this the slideways of these machines are not pressure fed either, at best the lube is designed to carry the load while it is present between the slides.

So a hand finishing process is resorted to, which by time honoured tradition renders the final work piece suitable for the job intended.

By the way, you wouldn't get much mileage out of a 600 grit grinding tool, due to it being rapidly glazed by even the smallest amount of work, and redressing the stone is a messy and time consuming business, but as a process and for whatever purpose, it can be done, even if It is not the time honoured way.
Ian.

To sum up this whole thread, "everyone will find their own way to heaven no matter how you perceive it".
Ian.

To sum up this whole thread, "everyone will find their own way to heaven no matter how you perceive it".
Ian.

Hello;

Do you have photos (magnified) of the surface after scraping ?

Thanks,

Kreutz.

Ian,
Thanks for adding the pictures most interesting.

Handlewanker had mentioned planing a surface prior to scraping. Oldmanandhistoy's method seems to fall somewhere between it and scraping, or perhaps an alternative to planing?

I will add one more process to my methods. That will be to hand SCRAPE the surface when the surface is near completion to attain the required surface effect. For a none sliding surface this extra process will be omitted.

The use of angle grinders for rapid stock removal has been mentioned more than once which included a reference from handlewanker. This is not in dispute; it is the final surface finish. The difference in surface finish is microscopic so there for only a minute amount of material needs to be remove via hand scraping to achieve the required effect. My quote above is just my way to heaven.

"everyone will find their own way to heaven no matter how you perceive it".
Ian.


By the way, you wouldn't get much mileage out of a 600 grit grinding tool, due to it being rapidly glazed by even the smallest amount of work, and redressing the stone is a messy and time consuming business, but as a process and for whatever purpose, it can be done, even if It is not the time honoured way.
Ian.

If you take a look at the picture in my first post you will see a rubber block, less than two seconds on this will refresh the wet N dry.

Ian, you may be interested to know I have another idea which includes the use of a rotary tool that could eliminate the use of a hand scraper. :D

John

AAAAGGGHHHHHH, he's at it again, quick where's my pills, gulp.
Now John it had better be good.
Ian.

AAAAGGGHHHHHH, he's at it again, quick where's my pills, gulp.
Now John it had better be good.
Ian.

It is at this point only an idea and as the saying goes “life is to short” so will very likely stay just that an idea. (wedge) :p

John

Hello;

Do you have photos (magnified) of the surface after scraping ?

Thanks,

Kreutz.

Hi Kreutz,

A picture would be interesting but I would guess unavailable. If I had the means to take such a picture I would.:)

Ian,

If you are still with us and your pills are still having the desired effect I wondered if you could take a look here http://www.desktopcnc.com/swarf/frosting.htm and comment as I would be interested to know your opinion.

Also I am at present using an old file ground, heat treated and finished on an oil stone as my scraper and would like to know what would be the ideal metal to use for a purpose made tool?

On an earlier post there was a brief mention of number of points contact per square inch depending on the application. What I would like to know is, is there a formula to calculate this number?

Finally I have just started investigating the use of Turcite B (see here http://www.midlands-slideway-grinding.com/products.html) for use on sliding surfaces on a milling machine and wondered if you had any opinion on this subject?

John

A On an earlier post there was a brief mention of number of points contact per square inch depending on the application. What I would like to know is, is there a formula to calculate this number?


you used to be able to get loupes with a grid on them to assist with counting - spot check a few squares and you could extrapolate contact points per sq inch

Hi John, Yes, I saw the artical about the frosting of slideways and totally agree, it's a decorative effect which adds no accuracy to the finished fit but looks good.

As far a a photo is concerned if you get down to the Macro level with a camera then this would be about as good as you can get, as if you go even closer you start to lose the ability to judge what it is you are looking at, and more or less will be seeing the grain structure of the material.

For many years now I have always supported the idea that static slideways, e.g. lathe beds etc, should be scraped to just clean up remachining and not "scalloped" for oil retention, as this just allows the dirt to get past the wipers and into the slide interface with the saddle, but the saddle should definitely be scalloped to hold the oil in contact with the sliding surfaces, otherwise the oil will be squeezed out and metal to metal contact will occur.
Any frosting, of the static surfaces, is a pure waste of time and only serves to impress the novices.

I haven't had the opportunity to come into contact with Turcite as a slideway material interface, but as a design feature it should have a lot of merit.

Some years ago, (1975) I helped a friend to construct a lathe from all mild steel parts, and the various interfaces, saddle/bed, crosslides etc, had brass shim material inserted, so that there would be brass to steel sliding faces wherever they occured.

This method worked very well, and 30 years later it is still operational, with no signs of the mild steel being scored by friction, which as the Turcite is a similar design feature it should also work extremely well.

Scrapers made from files work well provided you follow a few simple rules as for working with high carbon steel.
The cutting edge for a distance of 25mm (1") back, should be left glass hard and NOT tempered at all.

This is all you need for a long life cutting tool, and if you can hone 25mm off the end of a scraper in the course of a lifetime, you're definately doing something other people aren't.

The making, preperation and use of a flat scraper could fill a thread and maybe a new one should be opened to get the views of many on the subject, as it's a very valuable skill to have and once the basic fundamentals are understood the rest is down to practice.

You can do more damage with one flick of the wrist, using a scraper the wrong way, than if you left the job completely alone, even in a worn state.

As Macgyver said you can get a loupe with a grid to allow you to measure work at the 10X level, such as linear and angular dimensions, and I've seen them on Ebay for about A$25 from Hong Kong, but this is overkill as the 25 dots per inch is just a recommended level, and you soon get to recognise the difference by eye, so whoever dreamed that standard up was really nit picking.

Interpreting this practically, across the WHOLE SURFACE, and taking any one area of about 25mm X 25mm (1" X 1"), then you are getting there if 1/2 of the area is estimated to be in contact and shows faint blue traces which actually look grey.

Some time back someone showed me a piece of bearing insert material that was made from a mixture of sintered bronze and Teflon, maybe this was Turcite?
Whatever is used, the insert material should be anchored to the moving face and allowed to slide over the static face and thoroughly protected from the ingress of swarf particles.
Ian.

BTW John, what was the NEW way, (as long as it doesn't insinuate bringing the venerable scaper into the 21st cent), to supersede the scraper, I hope it's not a mini sandblaster, I just couldn't contemplate the notion.

Maybe it's a spark erosion type thingy that you attach to the two slides and the high points that make contact just get eaten away, no?
O.K. I'm just curious.
Ian.

Mr Handlewanker is talking out of his backside.

Here is a company in the USA http://www.galleryofmachines.com/index.html

That have been remanufacturing machine tools for 20 years

Very interesting is their way grinder that takes a finish cut of .0001"

A further quote from their website

We commonly hold .0001 per foot on our way grinders and can achieve .00005 per foot with extra effort. Ground machine components are periodically inspected with our auto-collimator capable of measuring one millionth of an inch in both the horizontal and vertical planes. The accuracy of our way grinders is extremely important since we use the ground components of the machines as masters and scrape the mating parts to fit. In many instances, this is the way it was done at the factory.

This is a quote from Mr Handlewanker

Furthermore, the grinder has not been made that can grind a perfect slide way, due to wheel wear, wear and tear on the machine itself and slideway clearancs that vary as the pressure of the work load comes on the work being ground, and in addition to this the slideways of these machines are not pressure fed either, at best the lube is designed to carry the load while it is present between the slides.

It says everything is you look at that lathe bed planer as to the quality you will get with that.

Phil_H

Ian,

Thank you for the added information. Just for the record I am guessing that at some point in your career you worked as a hand or during your working life were instructed by a qualified individual? As already mentioned my grandfather scraped metal for a living for over 40 years and now I really wish I had taken more interest when I had the opportunity.

Turcite B
http://www.dilanda.it/pdf_file/Busak+Shamban/Bearings%20and%20Bushings/Turcite%20B%20Slydway.pdf

Interestingly Turcite B is applied and then scraped in the same way as cast iron linear slides. If I can find it at a reasonable price here in the UK I plan to use it on my saddle and gibs.

I don’t wish to get involved in any more personal intercourse so will leave this thread at this point but will be watching with interest from the side lines:D and may jump in with the odd question. I would just like to say thank you to EVERYBODY who has contributed it has been/is appreciated.:wave:

John

Hi Phill, never seen it done, that is the backside bit you refer to, you seem to be an authority on the subject, how about you giving us a bit of your eggspeereeunce, do you remove the undergarments to blast or just stand and shake all over?
I.

I have just read through this thread and have a few things to say. I recently spent almost a year of my life building a small CNC milling table. All slide bearing sufaces were scraped. I purchased a book and video on the scraping process, which I would recomend to anyone. http://www.machinerepair.com. In no way would I consider myself an expert on scraping, but I would like to share what I know. There are two "modes" of scraping, roughing and finishing. In the roughing mode you are just trying to romove material to restore alignment and to get the surface "close". In roughing, a slightly thicker film of blueing is used on the surface plate. As Ian mentioned, cuts should be made at 45 degrees to the direction of travel. A cut refers to rows of individual strokes side by side. In roughing strokes can be long(1/2 inch or so). In finishing, strokes lengths are reduced to 1/4-1/8". A lighter blueing film must be used when finishing. Otherwise, the layout fluid will sqeeze into the low spots and give a false reading. When finish scraping lighter downpressure is used. Between each cut, the surface is usually deburred with a medium to fine stone. This levels off the peaks and gives the suface its final contact area. The cutting action down with the hand stone is different than that of a surface grinder. It is done at a much slower rate always in the direction of travel. This minimizes the "ploughing" action.

Scraping is just a refinment of the original bearing surface. Determining when to stop is aplication dependant.

Zac

Between each cut, the surface is usually deburred with a medium to fine stone. This levels off the peaks and gives the suface its final contact area. The cutting action down with the hand stone is different than that of a surface grinder. It is done at a much slower rate always in the direction of travel. This minimizes the "ploughing" action.

Zac

Hi Zac,

Thanks for the post and sharing the info. :)

I find the above quote very interesting; just to be sure I have this correct are you saying that a “medium to fine stone” is used not only during the scraping process but also at the end to give the final finish? Does the book only say to use a “medium to fine stone” or does it give more detailed information such as the type of stone?

John

To quote Michael Morgan, the auther of the book, "When a part is still being scraped for alignment or "roughed in" , a file or rough stone may be used for deburring.As a part is becomes closer to finishing, successively finer grade stones are used."

and then "Deburring during this (finish) stage is done with a much lighter touch. The goal is to remove only the scraping burrs and no other material."

From my novice experience, I have found that very consistant deburring is required to give a good finish product. I have been using a small knife edge stone that is about 4in long and tapered in thickness-about 1/4 down to 1/8". The book has a lot to say about the way you hold the stone. Any down pressure applied to the stone off the edge of the part will cause a rounded or tapered edge. If you deburr to much-especially in final stages- you end up "losing" the surface you just worked so hard on.

To quote Michael Morgan, the auther of the book, "When a part is still being scraped for alignment or "roughed in" , a file or rough stone may be used for deburring.As a part is becomes closer to finishing, successively finer grade stones are used."

and then "Deburring during this (finish) stage is done with a much lighter touch. The goal is to remove only the scraping burrs and no other material."

From my novice experience, I have found that very consistant deburring is required to give a good finish product. I have been using a small knife edge stone that is about 4in long and tapered in thickness-about 1/4 down to 1/8". The book has a lot to say about the way you hold the stone. Any down pressure applied to the stone off the edge of the part will cause a rounded or tapered edge. If you deburr to much-especially in final stages- you end up "losing" the surface you just worked so hard on.

Thanks again,

That’s cleared that up and it is the first I have read about the use of a stone during scraping.

One of the main problems I have is keeping a good sharp edge and this is with a scraper (old file) that has been hardened. I know now that this thread has come about because of the quality of cast iron in my mill. There are some surfaces that even with a freshly honed tool can not be worked with a scraper as it will just skid over the surface. Take my column as an example; one end will scrape with ease but right at the other end I cannot touch it via conventional means and have no other choice but to use my grinding technique. You live and learn I suppose.

John

i was taught, and it works well, to break off a section of file maybe 4" long. grind most of the teeth off. run this over the work, no real down wards pressure, like you are wiping off a counter. some stones would be in appropriate for this as they could leave abrasives in the soft CI, something like a hard Arkansas would be OK but IMO the file is better. it is a deburring app not polishing like Belding says and the file will do a better job of catching and breaking off the burrs

Hi all, I second the "deburring" between scrapes that are being mentioned.
When the scraper is working it accelerates forward under hand pressure and comes to an abrupt stop, usually without being lifted and so a "burr' is thrown up, only miniscule, but when you come to test the surface on the plate it is this burr that will contact first, apart from the fact that it puts your teeth on edge as it slides on the iron plate.

I've always used a fine square brownish type stone, probably Arkansas, that broke off of an oil stone and served the purpose well.

BTW, if anybody has an oilstone that has been well worked with the end of a scraper, to such a degree that it is grooved and useless for anything much, it can be refaced by going outside and finding a flat cement paving stone.

Using two hands, rub the oilstone on the paver, as if you were scrubbing the floor, untill the surface is worn down a bit and all the grooves are out.
Remember to turn the stone end for end to even out the wear and get it parallel to the other side.
After that treasure it, good oilstones are dear to come by.
This is one of the reasons the edge face of the oil stone is used to sharpen a scraper, because it isn't used for anything else, and doesn't damage the top face used for other tools.

I always use Kerosene to lube the oilstone when doing ordinary sharpening, never engine oil as so many do, otherwise you just clog up the face of the stone and the metal particles form a goo, also the stone cuts cleaner and faster.

Hi John, one of the problems you could be having in keeping the scraper sharp is because the end is too thick.

When the scraper is forged down it doesn't want to be more tha 2mm thick when ground and sharpened.
More than this and you will spend the best part of your shapening time removing excess metal.

When the scraper is presented to the stone, vertically, it leans to the left at about 3 degrees.
The left hand holds the handle vertical and the right hand grips the end between thumb and forefinger, pushing the cutting edge rapidly back and forward so imparting a curved cutting face on the end.

After a half dozen strokes the scraper is rotated and the second face sharpened the same way.
When viewed end on, the end now has two distinct faces on it, 1mm wide, like a very shallow arrow head.

The secret is to sharpen often otherwise you rub a hard skin and get nowhere.
A scraper is sharp when it scrapes a burr when applied lightly to the thumb nail.
Ian.

any1 like to put out a vid on ebay of you scraping some plane.
or even better scraping two or three planes to absolute square/parallelness.

Excuse me i'm not trying to be rude(quite the opposite actually)but it doesn't matter how many times i read the mysterious steps of handscraping i can't even imagine yet.

I remember meself going crazy readig articles three times over until i had to give up cause i just wouldn't get it without any clear pictures i guess.

if this is magic and yall warlocks keeping out on us ,don't curse me please.

Irondigit,

Check out http://www.machinerepair.com/video.html, there are three sample clips from his video. Keep in mind that this process takes a lot of patience, but the end result is worth it.

thats nice belding thank you.

the damn 2sec. of film told me more bout scraping i learned in days of reading.
Iguess its one of them things probably any1 could do with the right attitude and commiment.

I'M WRITING THIS IN BIG LETERS : ITS ALL ABOUT HOW LONG IT WILL TAKE YOU.Months or hours ?

i would still love to know more about scraping square/parallel and so on cause thats were my own imagination goes totally blurry.

mind boggling.

iron, i agree; anyone can do it. imo its not an art, its a technique and a process...anyone willing to acquire the knowledge and then patiently apply it should have success. most of all (if you don't have biax) its one tired arm.

if you really want to understand it, get Connelly's book, machine tool reconditioning. Mostly its a comparative process. yes, getting things parallel is a bit tricky, and square more so....but its far from black magic. I gave you tenths indicator & base, could you determine if two surfaces are parallel? what about a master square, surface plate and indicator, could you measure how square something was? at the risk of oversimplifying, scraping is a very controlled way to make a surface flat by comparing it to another known to be flat...its just a way to remove material in a very controlled and localized manner...checking for parallel or squareness is a metrology exercise, same as if if you ground, milled or filed it. you use these metrology techniques iteratively with scraping; scrape, check, scrape check etc.

i just keep hoping someone will log in one day and write the secret right down for me to leech

but seriously i guess i was just looking for a way to do this without the appropriate(read expensive to me)master surfaces and squares.

still i'm sure one day i will take a swing at this most admirable and proven technique.
My metrology just ain't up there yet and until then i'll be lurking.

thx for sharing guys.

Hi John, sigh, once again I will state, not out of wanting to be awkward but just to produce the end product as is required, that if you use ANY ABRASIVE method you will by the nature of the abrasive material make a ploughed field, (multiple vee grooves) of the surface and this will leave you with millions of sharp pointed crumbly peaks that under the sliding of one piece of metal on another just shear off and so you end up with a rapidly lower, although miniscule, area of non support.

Abrasives will produce grooves and sharp jagged peaks, whereas scraping will result in a series of undulating hills, more condusive to oil film retention and load bearing.

Ian.


Read this whole thread with great interest. I have a well worn bridgeport that I would like someday to tackle. I have no experience at all and have read everything I can find on the subject of scraping and other possible methods. The table has the usual sag that no doubt will require a lot of material removal to correct.

Now for the probably dumb question. Wouldn't the sharp peaks, grooves etc. described above show up when the part is blued up against the surface plate? The pictures of the "dremel" method surfaces appear to be lacking any such sharp edges or grooves, just a nice oval spot pattern.

Also, I read that the scraping method also leaves sharp burrs at the end of a stroke thus the need to lightly stone the finished hand scraped surface.

What am I overlooking?

Read this whole thread with great interest. I have a well worn bridgeport that I would like someday to tackle.

Hi,

A bit late replying to this as I didn't get an email reminder.

I would say if you have an old Bridge port the iron will be of good quality so I would stick to conventional methods.

If you want to give my method a go for removing iron faster you could always finish off with a scraper.

Good look,:)
John