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Thread: Way lapping, Scraping, Gib adjustment and Lock screws

  1. #109
    Registered BobWarfield's Avatar
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    Cruiser is right, and it can improve the accuracy of the machine because it allows you to run the gibs more tightly.

    Chris D, we're not talking about lapping a machine hand scraped to precision. We're talking about machines usually just milled and sometimes that not very well. The amount of lapping involved is not sufficient to remove enough material to reduce the accuracy, but it is sufficient to allow the ways to run more smoothly and hence to let you adjust the gibs tighter, which results in more accuracy.

    Such are the compromises on these cheap machines. Yeah, it's horrifying to "professional machine tool builders." But in the end, go with what works.

    Cheers,

    BW

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  2. #110
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    I disagree. Lapping ways by sliding the saddle back and forth induces more wear to the middle of the traveled portion than the out side areas. This depression ends up causing a looser fit in the middle and tightness at the ends. Premature wear is the result of lapping. Hand scraping is HARD. it takes real effort on top of craftsman diligence at checking and rechecking progress. I don't have the strength for it. Being disabled I chose a different method of bringing the ways on my X2 to a better finish than the raw machined surfaces it came with. I used a knife profile second cut mill file.

    The smooth flat surface of a second cut mill file lets you lay it across the entire surface for a full engagement. The knife edged profile allows the file to get right into the root of the dove tail so you can scrape/file the entire surface. Indiscriminant filing will cause worse damage to your ways than using lapping compound, so you don't go crazy and just file away. You want to check the surface just like you would when hand scraping. I like that an 8" double cut knife edge mill has a little flex to it. You can lay it flat, raise the handle just a little bit, then use your other hand to apply downward pressure as you slide the file. Because of this slight flexibility you can address problem high spot areas without over filing a lower area. Yes, it takes craftsmanship to file in the right areas, constant checking to find those areas, and knowing when to stop, but it is more precise than lapping, and easier on my disabled hands than scraping. My X2 is very smooth across it's entire range of motion now with no tightness anywhere with properly adjusted gibs.

    If I could, I'd hand scrape. I can't so I precision filed. Seeing the surfaces after lapping turns me off to the entire process of way lapping.



  3. #111
    Registered BobWarfield's Avatar
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    Quote Originally Posted by MrWild View Post
    I disagree. Lapping ways by sliding the saddle back and forth induces more wear to the middle of the traveled portion than the out side areas. This depression ends up causing a looser fit in the middle and tightness at the ends. Premature wear is the result of lapping.
    How do you know?

    That certainly wasn't my experience, Cruiser's, or that of a lot of others who've lapped their ways.

    If you're doing it right, you're not going to add enough wear to do anything but smooth the rough travel of the gibs and ways.

    I would definitely lap before I'd take a file to the ways.

    Sincerely,

    BW

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    Using WEAR as an argument is down right ridiculous. If you take a pair of machined surfaces and slide them to each other repeatedly then you have wear till the surfaces mate, and by mate I mean that the highs are abraded off till the surfaces average out and the surface area of contact increases to that of the equivalent which has been ground true. Even the scraped surfaces do the very same thing, the highs reduce till the surface area in contact bears the load and wear reduces to a minimum and longevity is seen as a benefit. Wear will be the highs when fresh surfaces are in friction. As the surfaces mate and the surface area averages in, the wear reduces to a minimum constant with the exception of contaminants abrading between the surfaces.
    Lapping in of surfaces if done with long strokes will accelerate the wear of the highs till they flatten out. this is why lapping is so common and easy. this is why lapped in valves are so common with engine heads, It mates the two surfaces to each other to eliminate irregularities and bring them into the same plane.
    any machine that is ground or hand lapped is going to be better than the low end units indead, NO ARGUMENT. But, a rookie Scraped machine or even a rookie ground machine would most probably be CRAP. The same holds true with lapping, but, lapping will be easier and much less technical to achieve a useable machine. And as with anything, If done correctly, it works.
    Wear is not only a destructive element but also a tool to achieve perfection.

    Don
    IH v-3 early model owner


  5. #113
    Registered Chris D's Avatar
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    Perhaps I demand a bit more than the average guy - I am a machine tool builder by trade. I have been involved with CNC machine tools and conventional machine tools for over 3 decades. I worked as a tool maker, an applications engineer, service engineer and everything in between. I worked for Japanese machine tool builders, German machine tool builders, and Swiss machine tool builders.

    I can say without question, no where in the world would a machine tool builder "Lap in the ways" of any machine tool. You will continue to believe what you think is 'right' and I will never change that. However, I will continue to communicate that it is wrong, that there is no justification for it, and if anyone cares to prove me wrong, show me a real machine tool builder that "laps their ways in" to either reduce friction or improve accuracy!

    This is NOT an "old school" versus "New school" concept. If the "machine tool" is junk to start with, lapping the ways is not going to improve it or make it a "quality machine tool". If you think you are "reducing friction", okay, but if the damn thing has so much friction to begin with, it has more problems than lapping is going to cure.

    Those that believe they are doing something good by lapping ways will always believe in what they believe. Those of us who have worked with machine tool over the years, rebuilt machine tools, serviced them, and built them, know the reality - lapping is nonsense and advocated by people who do not have the knowledge or experience to be voicing an educated opinion one way or the other!

    Chris



  6. #114
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    i am no expert( not even experienced)

    i do understand both points of view.
    personally i would never lap the ways of my mill as i find it very uncontrollable process for my liking.
    i understand why in theory it is wrong and why the proper tools are not laped but there are people out there that do not have proper machines and lapping improved their cheap machines. they never said that they transformed them to a Bridgeport or something but if someones machine was loosing steps and after lapping it stopped and the parts that he builds do not have tolerance problems compared to before lapping it is hard to argue.
    if a machine has machining marks of .5mm that the surfaces grab to and you can feel they do not move maybe lapping makes the sharp edges smoother and tables start moving reasonably then why not. even if it creates an inaccuracy of .3mm on a machine that did not work at all it is an improvement.
    at another thread i asked why dovetails or box ways and not linear bearings. to me i would not scrap or lap or do anything like that. if i wanted a real improvement for my mill i would trust skf or another proper company to give me the tools to do so. but that is me a not experienced machinist that does not know how to do one or the other.

    at the end imo if you want a proper machine you find a way to save money for it.
    if you cannot then you start compromising. a compromise is connected to every persons priorities-finances-needs-abilities-believes-likes-etc.
    if you have the money you pay a tool maker to fix your cheap machine. if you do not you start looking at other options.
    lapping is just one of them to do what you want.

    it is highly unlikely to go around the world on bare foot but if you cannot afford flying on foot will get you two steps closer to the target.
    cheers from down under



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    Chris
    When I put together my shop I did not have large money to buy the best of the best. I had to make do, as do many others. As for term of service, I have been around machinery all my life. All manner of machines including wrenching on F100 jet fighters in Viet Nam, and 30 yrs running a multitude of machines as a machinist. When it comes to top dollar machines, I agree with you whole heartedly. But, We are dealing with the Chinese who don't necessarily know what QC stands for or take Pride in what they do. If I had found the things I've found with my machine in a high dollar machine I'd be making some lawyer very rich from the legal matters.
    When it comes down to being able to take a piece of crap and turn it into a silk purse, Well, that is what I do best.

    Don
    IH v-3 early model owner


  8. #116
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    A knife edged mill file is not going to break the bank. How about two word pictures. Looking at the front of the X2, lets admit that there are peaks and valleys running right to left on the Y axis saddle dove tail bearing surfaces. Pushing the saddle front and back while lapping takes some material off the peak, but the mating surface has a valley eroded to match the eroded peak. The valleys allow the mating surface to come down until there is full contact across the surface. It isn't flat, it's just kind of mated more or less.

    Now look at the same surface from the side and note the stroke. More surface slides past the middle of the base, than the front and back surfaces see. Unless you are sliding the saddle right off the base, and keeping that saddle perfectly level, the front and back portions of the base will NEVER be level with the middle. Does it matter? Only if you are a craftsman. if you are just a hobbyist plunking around and playing, no, it will work just fine. For me, it's knowing it isn't as perfect as I can make it with my abilities. If your craftsmanship level of ability is smearing on a paste and stroking the saddle back and forth, hey it seems to work for a lot of people.



  9. #117
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    This thread has left me with more questions than answers. I have an X2 mill which binds near the very end of the Y axis (at the handle end, before the saddle overhangs the base), no problems anywhere else and accuracy of the usable portion of the axis seems good. Whatever method I use I only want to remove metal from the 0.5" long trouble-spot, and it's clear that lapping will not do that.

    I am trying to decide if it's worth attempting to scrape such a small area, or would I be better off just carefully filing or sanding it down. If I carry on as it is will it get worse? I am completely new to this so any advice is appreciated!



  10. #118
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    This problem could be caused by a bump. Not a bump in the part exactly, but bumping the part's way surface while everything was in pieces. The said bump might have raised a divot in that one area and the small imperfection causes a binding. A flat knife edged mill file is PERFECT for smoothing the divot down. A few strokes is all it probably needs. In fact, by lightly sliding the file on both right and left surfaces ALONG with the dove tail gib areas, you might even feel the roughness. (not all surfaces at the same time, but making sure you check/file all surfaces. Sometimes the problem isn't on the way, but the gib area.) You don't need to be aggressive to file it down, just some smooth strokes holding the file flat to the surface you want to bring into conformity. For your problem, I'd shy away from lapping the surfaces completely. You obviously don't want to wear more of the middle away.



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    Quote Originally Posted by MrWild View Post
    This problem could be caused by a bump. Not a bump in the part exactly, but bumping the part's way surface while everything was in pieces. The said bump might have raised a divot in that one area and the small imperfection causes a binding. A flat knife edged mill file is PERFECT for smoothing the divot down. A few strokes is all it probably needs. In fact, by lightly sliding the file on both right and left surfaces ALONG with the dove tail gib areas, you might even feel the roughness. (not all surfaces at the same time, but making sure you check/file all surfaces. Sometimes the problem isn't on the way, but the gib area.) You don't need to be aggressive to file it down, just some smooth strokes holding the file flat to the surface you want to bring into conformity. For your problem, I'd shy away from lapping the surfaces completely. You obviously don't want to wear more of the middle away.
    Thanks for the tip. Can't feel a divot by hand but I do think filing will be the way to go, when I feel confident enough! Just need to work out which side or both needs filing.



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    If one is going to file cast iron then there are a couple important things to do, one is to keep the file clean by brushing it every couple of strokes. two is get some white chalk and give the file a stroke with it to help keep the fine from loading in the files teeth. another is to never ever as in NEVER back drag the file as with any tool this will dull it in no time. Last is if the file is not new, hold it up with a strong light and see if light reflects from the cutting edge of the teeth of the file. If you don't know what i'm saying then take a known used abused file and try it ! A dull file is useless.
    lastly, when filing insure there is no oil or grease on the base being filed. some carb and choke spray will degrease it pretty good.
    one fine point is when done take a bit of leather and some moly lube and rub it into the degreased iron, don't leave residue but insure it is well stained with the moly. then oil and slide away.

    Don
    IH v-3 early model owner


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