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View Full Version : Yet another iron in the fire...



BobWarfield
06-23-2006, 05:47 PM
It's been taking me so long to finish my CNC lathe conversion, that I broke down and ordered Aaron's CNC kit for my IH mill. He has them on sale at a decent mark down until end of the month, so I couldn't resist.

The lathe really isn't that hard a project, but between how little time I find to get into my shop, other projects (like getting the IH mill stand built and the mill running) and my usual over engineered approach (fancy control panel, GRex, and the works), I thought a short cut on the mill conversion might be a good idea.

Will keep you posted after I get the kit and get going installing it. Just so you know, I am not likely to start on it until after the lathe is finished. I just wanted to cash in on the good sale deal.

Best,

BW

Switcher
06-23-2006, 06:08 PM
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Ron111
06-24-2006, 09:28 PM
Bob,
Do finish the lathe, I want to CNC maybe a Lathemaster Mill (which is simular to the IH), I don't think that I am knowlable enough to do it with the servo motors, so I'll most like stick to the stepper motors. Has anyone put together a good tutorial on servo motors? Maybe I could study up, and venture out on new ground. But I guess I should be asking questions like the advantages of using Servo's over steppers. Is it only speed and possible the fear of loosing steps with stepper motors, or are servos more accurate?

Anyway, do you have an active thread on the lathe or is it on your webpage and is it your lathemaster or are you building one from scratch?

Look forward to whatever your building.

Take care,

Ron

BobWarfield
06-24-2006, 11:49 PM
Ron, you can track my CNC Lathe activities on my blog:

http://www.thewarfields.com/MTLatheCNCBlog.htm

as well as the home page for the conversion:

http://www.thewarfields.com/MTLatheCNCHome.htm

The project moves in such fits and starts (especially compared to your recent rapid progress!) that I don't think it's worth a thread here. Last guy that was so slow got chewed out over it, heh. I'll send up a flare when I get it done so people can check it out.

My latest activity today was to design an optical limit that I'll be testing for potential use with the lathe. The biggest holdup is I like to open way too many cans of worms at once. But what the heck, its a hobby, eh?

That Lathemaster ZAY mill is almost identical to the IH mill I have. Just a little smaller travels. Go through the IH web site carefully, as most of what is there is well documented and totally applicable. You can even install the same kit Aaron sells.

As to the advantages of servos over steppers, whew boy, there has been a lot written about that! First thing you have to do is separate out the encoder as a servo advantage. You can add encoders to steppers, and in fact Mariss over at Gecko has a very cool project underway whereby you will be able to do exactly that and tie it back into the GRex motion controller to make what he calls an "unstallable stepper". No more lost steps!

Probably the second big advantage is a much broader torque curve. Steppers peak out at 1000 rpm for the most part and then decline pretty fast if you try to go faster. You will want to design your drive ratios so the max torque is happening at your fastest likely feedrates. You may get a little more speed on rapids, but going for the really high speed rapids can be hard due to the limited and peaky torque curve of the stepper.

A big disadvantage of servos is they are just not as standardized as steppers. That means you've got to do a lot more research and fooling around to work with them. A cool thing about the Gecko products is they all work on step + direction signals. Depending on what driver board you by, you can run steppers or servos. I suppose you could even mix them.

I don't know if I'll ever get to messing with servos or not. Steppers are a lot cheaper, and the unstallable step drivers seem like they kill nearly all the stepper warts. We'll have to see.

Best,

BW

widgitmaster
06-25-2006, 02:38 AM
Just returned from your Blog!
That's a nice setup you have there Bob!
I can only dream of having that much floor space!
Oh yea, and a heat-treating oven too!

Eric

BobWarfield
06-25-2006, 08:43 AM
Thanks Eric!

No heat treat oven as of yet--it's just a gleam in the eye. I want to build one, and it doesn't look terribly hard since the PID temperature controllers are cheaply available on eBay.

Widgit, there is surprisingly little floorspace in the main shop, actually. It looks just about identical to the space of your shop. The downside is I could never have fit that big knee mill you've got through my door. It's a normal sized door, but only 2/3's height, and there is a 2 step drop followed by an immediate sharp turn. The IH mill is what fit, and I'm very happy with it.

The welding would be impossible if I wasn't using the top of a car lift as a hide-away workshop extender.

Eric, I had a thought for you. I know you make the nice T-slot tables and offer them on eBay. You should put together a fixture plate setup. I've been making notes on one here:

http://www.thewarfields.com/MTMillFixturePlate.htm

You could offer the big plates in a size that makes sense for commonly available mills, as well as accessory plates of a size for Kurt Vises and rotary tables. A T-slot plate would also be handy to drop onto the main fixture plate from time to time. It would need to be done from cast iron to avoid the electrolysis messing up your mill table, but I'll bet you would get some takers for these, especially among the CNC'ers.

As you can see from that page, I'm planning a design similar to what Anvil uses. Still debating 3" versus 2" hole centers.

Best,

BW

Ron111
06-25-2006, 09:02 AM
Bob,
Did you buy the kit from IH that just has the mechanicals? And are you planning to use steppers? And allow me to ask, I read where the guys are lapping the ways of some of the mills. I remember lapping valves, when I was a kid fooling with cars and motorcycles. Exactly what does lapping the ways do for us. The reason I ask, I have a shopmaster 3 in 1 and I having a unusual sound coming from the ways on the Yaxis(which is the long axis on that machine.) I think that I saw where some one recommended removing the gib and sanding it down a bit, but havn't run into the post again. So, when I read that some were lapping ways, I thought that maybe this would work for my anomoly.

Thanks,

Ron

Ron

Mcgyver
06-25-2006, 09:44 AM
lapping with a cone shape will work, but not with a flat UNLESS you are using a lap, ie you know and control the shape of one of the surfaces - lapping is a specific process requiring methodology and some skill, it is not putting abrasive compound into mechanical works and hoping for the best. lapping machine pieces to each other would be like pouring lapping compound into your crankcase....yes it will definitely loosen things up, but its only doing so by creating slop, and we don't want that in the bearing surfaces our engines or machine tools!

this subject came up a while ago and is covered at depth here, hope its of use.

http://www.cnczone.com/forums/showthread.php?t=11874

BobWarfield
06-25-2006, 03:26 PM
Ron, you have a unique talent for asking the controversial questions in such a matter of fact way.

Which is better, servos or steppers? :boxing:

What about lapping your ways? :boxing:

Both have been the subjects of long and somewhat acrimonious threads here in the past. I see McGyver is getting the gloves on early with respect to lapping. As he points out, lapping, at least in this case, is not about getting things flatter, straighter, or truer. In fact, if you look at the amount of activity Aaron recommends in his lapping instructions (i.e. grit versus number of strokes), it couldn't possibly move that much metal to make a profound difference there one way or the other (and here is where I'd best have my mouth guard and helmet in place!).

A short conversation with Aaron will quickly get you to the bottom line on why he advocates lapping these mills. In his view, it allows you to run the gibs tighter, which he says will result in greater accuracy. For the manual machinist, it lets you run tighter and still maintain smooth motion. For the CNC machinist, it allows you to really tighten things up and let the torque on your steppers or servos still be able to deal with it.

I have ordered the lapping kit along with the mechanicals only CNC conversion from Aaron and I do intend to lap per Aaron's advice. He knows these mills inside and out and swears up and down that it improves their performance, which is good enough for me.

I am sorely tempted to measure this machine according to Tormach's QA spec both before and after lapping to see what the measured difference is, if any. I think that spec provides a pretty complete accuracy work up on the machine and the result would be fascinating. At the least it would move things from the fight between, "Trust me, this works," and "Lapping will always make your machine less accurate and must be avoided like the plague, period," to something were there are real numbers to determine the real impact.

There is just one little fly in this ointment. I really hate the thought of tearing the machine down twice, and if I don't compare pre and post lapping while the machine is manual, the results won't be nearly as meaningful. If nothing else, per Aaron, I will be able to operate in CNC mode with the gibs really tight. Some will still say the proof is in the pudding, while others will argue that any increased accuracy came from a switch to ballscrews or some other source and the numbers are therefore meaningless. This would mean I've got to tear the thing down twice to get objective numbers done and do the CNC conversion. First I go through the measurement regime Tormach uses. Then I tear it down, lap it, reassemble, and measure all over again. Then, I tear it down, convert to CNC, reassemble, and probably measure that again too.

This all seems guaranteed to completely stop all forward progress I'm making on any other projects, so I am not exactly sold on doing it yet.

Best,

BW

Mcgyver
06-26-2006, 08:12 AM
no gloves Bob, and no malice or acrimony. I was trying to share knowldedge, how one proceeds is up to them - it doesn't make or wreck my day :) good luck with it.

BobWarfield
06-30-2006, 12:48 PM
Quite allright McGyver, I don't take offense at any of it, I just know these topics spur strong feelings on the boards and was more letting Ron know than anything.

BTW, I've come across several of your projects lately that looked really cool. for example, your sharpening jig projects and some of your CNC work. Please keep up the great postings. I'm very inspired by it all.

Right now I'm tied up with Widgitmaster's Kurt vise stop gizmo. Fussed and fumed for a bit before deciding I had to make one. I note that you use the collet-style clamps on some of your projects. I've wanted to try making some, so that's what I'll be doing for my vise stop.

When I get done with that, I will probably start building a sheet metal pan brake (I told you I had come across your postings!). I like the picture you posted over on HSM so much I tracked down the book the brake originally appeared in. Looks straightforward to build, and I've got the steel ordered already. Guess what I want to use it for? Enclosure work for my CNC. Now having seen your enclosure post, it does seem like this is a small world that just turns round and round on very similar thought processes!

After seeing all these common threads I finally just looked through all the posts you and Widgitmaster had made. Just trying to get some ideas and knew you guys tend to make high quality posts. Thanks!

Have a great weekend all,

BW

Mcgyver
07-02-2006, 12:42 AM
thanks for the kind remarks. which brake? I think i know the one you mean, wasn't mine though just posted the pic. beautiful build none the less.

The split cotters are easy to make and a functional way to clamp, you'll like using them. If you're not sure of the process let me know

I to have toyed with building a brake, I keep flip flopping between buying a good one (used) and making one. I've a 4' 16 gauge brown boggs shear that must weight 1000 lbs and a home made pinch roller, all I need is the brake and spot welder and I'm good to go with sheet metal. well at least until i want to make a fender or some bloody thing :D

BobWarfield
07-02-2006, 01:11 AM
Yeah, it's the same style brake as the pic you posted. The plans were in the Metalworking Vol 2 book. The pic you posted was finished a lot nicer than the one in the book. We'll see how mine turns out. I'm scaling it up a bit, to 24" instead of 17. This was the picture:

http://www.thewarfields.com/img/Toys/MachineTools/OthersProjects/BoxBrake3xx.jpg

I'm doing the split cotters the way Lautard describes them, with a flange to hold them while you bore, then you turn the flange back off again. So far so good. I'm waiting for some steel to arrive before I can do the broing operation.

You're going to need an English Wheel if you want to make fenders. I'd love to play with one of those. I liked the one that was featured in the magazines recently.

Best,

BW

Mcgyver
07-02-2006, 10:02 AM
Thats the one - it was made by Gary Hart who posts at the hsm board. he did a beautiful job of it, makes it compelling to have a go at it.

most times with the cotters, I thread the cotter, then use a piece of ready-rod and a nut to hold it in place tight against the bottom of its hole while the intersecting hole is drilled/reamed. face a bit of the cottered end for clearance, then face the cotter to length - same idea as what you described, but saves having to turn the shoulder

Geof
07-02-2006, 10:29 AM
.....I'm doing the split cotters.....

.....most times with the cotters.....

Excuse the butting in question but you both used the word 'cotter'; what's a cotter? The context in which you use the word and the description for making it does not jibe with my understanding of the word.

philbur
07-02-2006, 05:19 PM
A cotter pin looks like this.


Excuse the butting in question but you both used the word 'cotter'; what's a cotter? The context in which you use the word and the description for making it does not jibe with my understanding of the word.

Mcgyver
07-02-2006, 10:39 PM
Geof, yeah like Phils pic. here's two i did recently, one on the shaft holding the tooth rest and the other the shaft holding the drill stop. I'm betting someone of your experience has seen/made dozens of these before? i've only ever known them as cotters from plans and books from both here and England, don't know if they're called anything else.

Geof
07-02-2006, 11:37 PM
Thank you to philbur and Mcgyver and apologies to Bob for the hijack. I hope you find it worth reading.

Cotter Pins; an overview by Geof

The first picture shows my technicolor rendition of what I was taught is a cotter pin some 50 years ago; a round shaft with a smaller diameter thread on the end and a flat going from the thread diameter to the shaft diameter. My bicycle had cotter pins holding the pedal crank onto the pedal shaft which had a flat for the flat on the cotter pin.

I went Googling and found this: titled "semcycle cranks and cotter pins"

The nut is just to retain the cotter pin and does not add extra tension to it. To tighten a cotter pin, the pin should be tapped with a small hammer from the opposite side to the retainer nut. The nut should then be tightened (taking up the slack). Then tap the pin in again and tighten the nut, Repeat until the pin can no longer be tightened.

I could not find any pictures but you can see that this description matches my pretty picture. The source was this; http://www.unicycling.org/unicycling/hypermail/2354.html and the 'hypermail' threw me until I noticed the date; Wed, 13 Sep 1995 17:43:27 +0100 (BST) and the poster was in Cambridge, UK.

So obviously my senile old memory is not so senile after all; this is what I considered to be a cotter pin prior to arriving in Canada. My Googling also turned up what I discovered was a cotter pin in Canada which is the second picture. For obvious reasons I call this a split pin.

Now you guys have really thrown me into a loop. I am very familiar with your 'cotter pin', actually I should say a version of it shown in the third picture. We make these and use them for clamping aluminum fittings we make onto 7/8"stainless steel tube in a manner that gives a grip of about 40lb-ft torque, which will slip when overloaded but will not mar the tube; our name for them is Pinch Clamp (I know, not at all original, sorry). I based this design on the clamps used to hold round toolholders in the turret toolpost on Herbert Turret Lathes. I am sure the Herbert manuals did not use the name cotter pin for these clamps but I cannot check because I tossed them all out five years ago.

Incidentally Mcgyver you would win the bet and then some. My Pinch Clamp was designed and first made in 1986. To date I guess we have made around 100,000 and our current production rate is about 10,000 a year.

PS: My memory tells me somewhere I read that cotter pins, the bicycle version, where derived from steam engines with the cotter pin being used to secure the cotter arm to the cotter shaft with this assembly something to do with the steam valve on the cylinder; specifically the mechanism used to alter the point of cut-off. Google let me down on this one.

Mcgyver
07-03-2006, 12:27 AM
well i would have been surprised if it was a new one on you....pic # 2 is what i would call a cotter pin, pic three a cotter or split cotter (no pin), although you've refreshed my memory with pic 1, also what i'd call a cotter or wedge. I've seen the term on plans and in books from both England and NA, perhaps the term is incorrectly being applied, but what the heck if everyone is doing it. as often as not, to streamline production, I'll just go with a half cotter, half of what's shown in pic 3, it would have to be half a split pin by your parlance :D

I can't remember a specific part of a valve gear called a cotter, but that isn't saying much - there are lots of valve gear types and I'm not a expert. on multi cylinder engines there are definitely places like the where the cranks or lifts mount to the reversing shaft that could use wedge cotters (often tapers on models) and that would put a cotter as part of cut off mechanism - these would be high stressed areas like a bike crank - but for all i know cotter shaft is another name for reversing shaft. some of the big ends on the connecting rods had square holes with bearings secured by wedges - these may well also be call cotters