Lathe Choice?

If you want to sort out the machinists, take away all their digital readouts and put them on a Bridgeport with about .010 backlash in the two axis, and tell them to produce an accurate 5 lug bolt pattern of a specified dimension for you. See if he knows how or where to adjust the backlash. Put him on a manual metal lathe and tell him you want 3 equally spaced radial lines on the surface of a freshly faced piece of round stock, without changing setup, or give him a chunk of cork to hold and turn to contour shape and dimension, as for a handgrip.

RJ

Reply to
Backlash
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Is there any other kind? :)

This is not a test of machining ability. It's a test of mechanical drawing/geometry. Draw the print correctly, with the right origins, and there is no need to deal with play in the leadscrews at all.

When I dimension prints at work, I do them one of two ways.

First way is, if I'm giving the print to the shop, and I make it look as nice and neat as possible. The second way is if I'm going to be making it myself. Then I spend an extra 20 minutes thinking about which are the reference surfaces and what order all the cuts and holes are going to be made. The print winds up a lot uglier but the job goes faster. Plus, I get to

*look* like I know what I'm doing, when I'm working in a fishbowl with folks standing around, who really do know what they're doing.

The staff shop is right in the middle of the main shop, and has windows on all sides. And the real modelmakers can spot trouble a mile away, so I'm always on my best behavior there.

Jim

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Reply to
jim rozen

"tell them to produce an accurate 5 lug bolt pattern of a specified dimension"

I never mentioned using a print...

RJ

Reply to
Backlash

On 1 Feb 2004 07:34:37 -0800, jim rozen brought forth from the murky depths:

There is a difference between fish tacos and bearded clams. Gunner, have him take you to a bearded clam palace instead. MUCH more fun.

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Reply to
Larry Jaques

"Always work from a print" was the first rule taught me. It's served me well over the years - doesn't have to be a fancy cad drawing, doesn't have to be blue line diazo, but it has to

a) be a drawing

b) have dimensions

c) have tolerances of some kind.

This can be on a napkin if need be. But there has to be something. That's when folks get in trouble, they step up to a machine and start cranking the handles every which way, with no print.

Jim

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Reply to
jim rozen

I'm no machinist, and never claimed to be, but that's just silly. Is a machinist forbidden to use pencil and paper, or did you forget the smiley?

Pete Keillor

Reply to
Peter T. Keillor III

There may be some places that might happen, but they're damn rare. My biggest objection is that NONE of the dealers are located in the area that the auctions are held, second, instead of bidding "by lot" it should be by individual machine, so the dealers lose their advantage. Give me one reason that sobel, fricken etc should buy a lot of lathes, and if you want one before it's even off the floor, it's going to cost you 50 to 100% MORE than his bid. If it's an auction held for dealers, then they should state so, not say "PUBLIC auction", because it ain't. Dealers aren't in business to see everyone get the same break they get.

If they even read the limited information that comes with the asian machines, there's usually enough there to give them an idea of how to go about it, although the english is somewhat hard to understand. I have a buddy, programmer for a living, bought a 9 X 20 Grizzly, disassembled it, cleaned and deburred, now he's deleriously happy with it. Until he started playing with a Taig, he'd never run any machine more than a drill press before.

Brazing is a long ways off yet, it needs a lot more than that. Tailstock quill is missing, also the screw, cross slide screw is bent, beyond repair, Damaged gear in the carriage, maybe in six months or so I'll be able to put it in one piece and see if it even looks like a lathe. Then I can start brazing. On the plus side, the steady rest and taper attachment don't look like they've ever been used, and the chuck is a nice Skinner with both sets of jaws. Quick change box is ok, but both of the spring loaded pins are broken off, might have to get creative here to fix that. Had to hacksaw the cross slide screw to get it out, thinking stubbing it and remachining. At the same time, I'm going to add a lock for the cross slide screw, one of my pet peeves is when it creeps unless I hang on to it. So many missing and broken parts that I might as well modify it while I'm rebuilding.

Reply to
Lennie the Lurker

That's fine when you have a virgin piece to play with, but what do you do when someone brings you a cracked up stainless casting, you need 9 holes centered on the main bore, say 10 inch diameter circle? You don't have a print, and when you're done welding it back together, you're going to have to true the main bore first, then do the bolt circle. I wrote a short basic program that gives me the X-Y coordinates, but you have to work off the center, and backlash becomes something to remember. A lot of the work in the job shops is repair, and prints are something other people have.

Reply to
Lennie the Lurker

Part of the situation here is that dealers do buy in lots, because they have the cash to throw around and also because this makes it easier for the auction houses. I think sobel haunts the auctions near to him.

I've never gone to an auction so I can't say anything about them. But those dealers are in the business to make money so what are you going to do, demand that they sell a machine for the same that they bought it for? They'd be out of business in a month.

OK, but I bet you stepped him through the process, if not actually helped him with it.

Most folks buy a new nut from south bend, and then purchase a piece of acme threaded rod and silver solder it into the stub of the old one. Errol did that for one of his school machines, he has photos on a web page. If you sold the steady and taper attachment on ebay you could probably *buy* all the bits you needed from Sobel, those things sell for more than the entire machine sometime.

Jim

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Reply to
jim rozen

I'm afraid I'm going to have to come down on RJ's side here. His point was not lost on me. Print or not, tolerance block or not, a machinist is capable of drilling the five holed bolt pattern using a mill with not only .010" lash in the nuts, but any amount of lash. Assuming one would be happy with a dimensional description, say a 6" nominal bolt circle, a true machinist is capable of providing such a pattern with nominal sized holes that would fit a mating part. The print with the accompanying tolerance block is the instrument by which the buyer, for lack of better description, details what he desires, hopefully eliminating the possibility of miscommunication. In the hands of a fool, a print would likely make no difference. He would lack the understanding and skill to generate the part, and that is RJ's point, if I'm not mistaken.

All that being said, I, too, like prints, and expect one with the work I do. If no print is available, I expect any related parts be supplied to me so I can make decisions in keeping with a successful outcome.

Harold

Reply to
Harold & Susan Vordos

Yuh know, Larry, if I didn't know better, I'd say that's down right nasty!

Harold

Reply to
Harold & Susan Vordos

Precisely. The end result always depends more on the skill of the man working the controls than it does on the machine itself. I've seen some that were always looking for the fastest way, or a shortcut, and always wondered why. Seems to me to make more sense to slow down a little and do it the right way the first time. I watched one shop owner trying to save time by trying to turn .004" off the spline end of a hardened axle, then ended up setting up the tool post grinder anyhow, which is what he was trying to avoid. Would have made more sense to save the carbide inserts and use the wheel in the first place. Sometimes the slow way is the fastest. The machine can't make up for that, it has to be the man that's doing it.

Reply to
Lennie the Lurker

I repair a *lot* of parts, and I've learned to always sketch out what I'm doing, by hand. Saves a lot of trouble in the long run - trying to shortcut that particular step is like that friend of yours who tried to use carbide inserts to fix the splines on the axle.

Eventually it has to be done right. Might as well to it right the first time.

Jim

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Reply to
jim rozen

Harold, I understood his original point. However, like Jim, I make myself sketches for fairly simple tasks as well as more elaborate ones, and wouldn't intentionally handicap myself by working only in my head. My experience with machinists has been more for experimental development than repair or production. Because of that, I have found it valuable to make sure the machinist and I understand each other. Sketches are a good communication tool for that. I'm a chemist, not an engineer, so a draftsman or lately a CAD guy renders my sketched design into a print. I always visit with the machinist and go over any questions and suggestions, plus be available if anything comes up.

Of course, that's why it's my hobby. I got really tired of only getting to watch. Every R&D machine shop in my new location is stuffed with pristine HLV-H's, wire EDM's, manual and CNC mills, grinders, etc. I get a little green every time I set foot in one, but have always enjoyed working with the machinists. These guys would meet your definition of machinist.

Pete

Reply to
Peter T. Keillor III

My point was that this task amounts to translating from polar coordinates into cartesian coordinates.

Unless the part in question is mounted on a rotary table, the job reduces into drilling one hole at zero X, and a Y equal to the radius desired. Then there are two pairs of holes done at opposite sides of the axis.

If the job is laid out so the single first hole is the origin, then it becomes a simple matter to step one distance Y1, go +/- X1, then step the next distance Y2, and go +/- X2.

If things are really laid out correctly, then there is no need to back up on any axis at all, and the backlash problem simply goes away.

Here is where working with older equipment shines through, Lennie is 100% correct that it's the man, not the machine, that makes the job, and learning on leadscrews makes on set jobs up the 'simple' way to start. I do this even when I *do* have the advantage of a DRO, like at work.

One of my favorite experiences was the voc tech class I took years ago. There was one student who was taking the class just to get at the machines, for some prototype he was making for a patent application or something.

He would always jump on the 'best' bridgeport, the one with the DRO, and would even go so far as to break down somebody's setup if they had gotten there first and already begun working [1]. "This is a really important job for me, and I don't have much time, and this is the only reason I'm taking this class" were all the sundry excuses this fellow would make. The instructor permitted this atrocious behavior, and the other students groused amongst ourselves.

But I never really found it to be a hindrance, because the leadscrews on those machines were not badly worn and read true. I think in some sense this gets back to the original thread, because the folks who buy the new asian import machine expect there to be exactly *zero* lash in the screws, because the machine is "new, damnit." They wind up with a disapointment because they learn that leadscrews don't work that way. The guy who goes from an ancient lathe to a merely old one gets a pleasant suprise because the screws read true over more than a few tenths of an inch.

Jim

[1] I am now of course aware that guys like that are the ones who wind up with their safety shoes welded to the table, or their personal toolboxes fitted with a zerk fitting and pumped full of grease, or any other myriad revenges. I was young and innocent at the time.

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Reply to
jim rozen

Thank you Harold. I can tell you have the experience.. As a maintenance machinist, you have to be able to wing it with a production machine down with an obsolete broken part or parts, a shipping deadline looming, other machines down and waiting on you for evaluation of repairs, and a production manager/owner coming by the tool shop about every ten minutes asking !. If you're going to be able to fix it

  1. Do you have the materials you need?
  2. Can you get your help to unload that semi truck? He's cutting the blank stock pieces, by the way.
4 Is it going to take long enough that I need to relocate employees to keep them busy? 5 etc, etc

Now, if you were me, would you ask this man to have the QC/draftsman draw up a nice Autocad print for you while you sip your morning coffee? On the other hand, this is how I work. Sometimes I'm running the surface grinder, the lathe, and the Bridgeport all at the same time, standing in the middle of the work triangle to monitor them. This is my job. I thrive on it. I flat love it. There's other sides of machining other than job shops, production machining, and prints to work from. The production guys, now they get prints.

RJ

description,

Reply to
Backlash

No. JUst even up the playing field, if it's a public auction, NO LOT BIDS. It's as easy as that. If it's going to be a dealers auction, ALL LOT BIDS. But the crap of advertising "public auction" and having lots that a hobbyist can't afford is nothing but bullshit.

Haven't seen either of his machines. He's about sixty miles south of me, and in the Chicago area, and I WON'T drive down there. The only place I saw him was at the gliderport, but I won't be going there again.

Except that the steady rest and taper attachments are why I want the thing. The cross slide screw is already fixed, unless I have to make a new screw for it, and it's just as easy to make it as to buy it. Nut isn't a problem, I've gotta make a new quill for the tailstock, and I'm going to need the tap anyhow, unless it's a different size. Not having the quill or the screw, it might be up to me what I choose to put in. Good practice for me if I buy the Monarch I'm looking at, but I have no idea what I want something that big for.

Ebay and paypal are starting to look pretty shady, seems paypal can freeze your account, doesn't matter how much you have in it, and hold it for an unspecified period without anything you can do. Read their TOS, if there was ever a better way to rip people off, that's it. And paypal is doing it, no reasons given, TOS says no appeal, they've got your bank account and nothing you can do about it. Verrrry shady. From reports on another group, you don't get to talk to a human on the other end either, and any court actions will be in kkkalif. Nobody there I'd trust with ten cents of my money, not to mention any greater amount.

Reply to
Lennie the Lurker

Quite sure. Its Newport Beach for gods sake..a hybrid yuppie ville in Orange County.

One of the big fancy stores right across from the restaurant in question has this big fancy sign proclaiming Condoms Galore!...not far from the Starbucks...you can figure the rest...

Gunner

Liberals - Cosmopolitan critics, men who are the friends of every country save their own. Benjamin Disraeli

Reply to
Gunner

description,

Yep, sure sounds like they would, Pete. And with wonderful machines to run, too. You mentioned not wishing to handicap yourself by working out of your head. I generally do a (poor quality) sketch of things I want to make, too, even on relatively simple things. What it does for you is keep an original thought straight. Once you start cutting, sometimes things look differently so you make mistakes. by cutting to a new thought. A sketch keeps you seeing it by the same eye, so to speak.

Harold

Reply to
Harold & Susan Vordos

Well, I reckon that the printout in my hand is sorta like a print without the pictures. On a lot of the jobs that came in that we did have prints for, they would draw one hole then spell out "X holes on XX bolt circle". The program came in handy for that.

That one I don't claim as a friend, Harry Bohn was only his own friend, and he made good reasons for it. He was the boss.

Yup. If it means slowing down or taking a few extra cuts, it's still faster than screwing it up and having to redo it. Which is where most people screw up, trying to go too fast, taking too much, trying to hurry it. Realizing when you've reached the limits of the machine and it's time to use a different one is also a part of it.

But, it only points out that the man standing in front of the lathe can mean more than the machine itself.

Reply to
Lennie the Lurker

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