PDA

View Full Version : Evaluating an old lathe for quality ... for newbs



Fasttrack
02-28-2008, 04:07 PM
Hey Guys,

I obviously greatly respect all of your knowledge and i've posted several threads here asking about specific lathes and their values. I was wondering if we could get a thread going that describes for new guys looking to buy used machinery what to look for in a lathe.

Everything from approximate value of different lathes (not really important) to a couple of "tests" to evaluate how much life is left in a machine (VERY IMPORTANT!)

On my thread about the southbends, i got several good suggestions about what kind of wear to look for, where it would appear, and what it would look like. I sure would like to see a general set of guidelines for this sort of thing. The obvious thing that came to mind was checking for spindle runout - take a dial indicator and a bit of drill rod with you when checking on a lathe, and of course check for broken gears etc ... but what other "tests" are there?


Thanks guys! I think this would be helpful to not just me but several other of the new guys here too!

p.s. i've spent about 20 minutes searching but all the seach terms i can come up with brings up about 200 different threads :)

p.p.s. I just found a great resource for this sort of thing: http://www.mermac.com/advicenew.html

Still love to hear what you guys have to say though!

topct
02-28-2008, 05:45 PM
I read that article "after" I bought my SB9C.

If I had read that I would never have bought the thing. The spindle took two hands to turn. All, I mean all, of the wheels would not move or where so stiff to turn, no backlash could be felt.

It was sitting on a garage floor with a box of misc. whatever next to it.

$450 later it was on my shop floor.

The guy I got it from, who claimed to be a former metal shop teacher said some WD40 would loosen the thing up.

Rather than do that I took the thing apart all the way.

My first discovery was that the spindle was in perfect condition. Some new oiler felts and a proper oil and it will now spin with the touch of a finger and easily meets specs as to runout and end play.

I did not get any change gears other than a ratio that would drive what appears to be a barely used lead screw.

I was able to figure out how SB adjusted end play in the cross and compound feed screws and have been playing a little with that.

It did need a new shaft for the back drive, but a piece of G&P 4140 fixed that.

This lathe has turned out to be a real jewel as far as I'm concerned.

I am not saying that anyone should buy something like this. Just what happened when I did.

Fasttrack
02-28-2008, 07:21 PM
Well you make a good point - sometimes you can get lucky. Maybe the most important thing is to just have a feel for the situation and not let your excitement blind you!

Plus 400 bucks is less of risk than say 1500 for a larger lathe. I'd be more inclined to go out on a limb with a smaller lathe like that then larger ones.

I do have a question for you guys though ...

How would you feel if you were selling a machine and someone showed up with a dial indicator to start measuring TIR and etc? Would you be offended?

tony ennis
02-28-2008, 07:27 PM
Beginners without a mentor should:

1) Avoid buying a lathe off ebay unless it can be inspected before buying.

2) If you want a 9x SB or 10x Atlas (or similar) be prepared to spend $1000 minimum. If you don't have $1,000 don't consider buying a lathe - keep saving. The reason being that a lathe that costs a lot less than that probably needs repair or tooling. So you're going to spend a grand. You might as well get it all at once and know the pieces fit!

J Tiers
02-28-2008, 11:28 PM
I have a different approach.....

I do not buy on machine details..... I buy on a sort of over-all picture, and I do look at a few key items.

If the machine LOOKS beat on, it may very well be beat-on.

If the machine looks re-painted, AND NOT USED SINCE, I expect bad troubles, and I move on.

If the seller seems shady, I move on unless I know the item is something good, and can de-bunk his statements.

I LOVE dirty oily machines. They are often sweet under all that protective gunk. People pay good money for preservatives, but old hardened oil is every bit as good in storage......

If the machine looks recently used, but not abused, then I will look at a few key items to see what condition the thing may be in.

Lathe ways, of course, for gouges, apparent wear and scratches, any ridge as appears on S-B when worn.

Also loose hand wheels (loose bearings I mean) missing parts, evidence of cracks or clumsy repairs, stuff that shakes but shouldn't.

Of course, accessories...... or lack of them.

In the end, I buy on "potential", as I see it. But I bought that way before I knew what I was doing, also.

I have bought only ONE real lunker, an AA. Pure ignorance.... it sure did look like a lathe, and it even worked like one also, but not ENOUGH like one...... And another machine with a problem I knew about and assumed would be easier to fix.

The AA I sold to a guy who showed up, liked it and paid the asking without any questions. I had chased away a couple guys who I knew would not be satisfied, but this guy gave me no info on what he wanted to do with it.

The other machine, a die filer, I used, and sold to a guy who I told about the problem but who was Ok with it.

So I have not been burned by my "system" of buying on general appearance, seller behavior, and some detailed inspection.

I have come to realize that it is far easier to come up with a "deal killer" than it is to buy a machine. So I expect some troubles, the machine is used. I know that all "previous owners" have some form of idiocy about repairs.

I just want to avoid the worst. And I have.

rdfeil
02-29-2008, 01:40 AM
Fasttrack,

It might just be me but I would be ecstatic if someone showed up with a toolbox (padded of course :p ) full of accurate tools and indicators. To me that means that the machine will get a new home with someone that appreciates machinery. BUT, I would carefully observe the potential buyers methods for evaluating the machine. It might be an elaborate scam to impress you to get a better price etc :(

Robin

wschoenbeck
02-29-2008, 01:05 PM
I bought my SB9A from the equipment dealer that I bought my Clausing 8520 mill from. A local guy here in San Diego who sells new Track mills among other things but also buys used equipment and buys out machines from defunct business's.

I guess I'd say my evaluation methods are similar to Jerry's. I took an over all look at the machine and checked the ways for wear (there was some as the lathe was shipped in 1957 hey' its younger than me :D ) but no gouges, severe scratches or ridges. The spindle turned freely and smoothly. The lead screw however did not. The seller took the QCGB and lead screw off for me and the screw and gearing turned freely. Problem was in the apron casting which had cracked in the area that holds the worm through which the screw passes as well as the key that provides power for longitudnal and cross feed. The worm was binding in the casting. It had been poorly repaired and then re-cracked. Seller offered to braze the casting back and bore out and re-fit the worm. No extra charge. I paid $1000 for the machine with a few bits of tooling (3 jaw, 4 jaw minus the top jaws, steady rest, milling attachment, drive plate etc) and I'm sure he worked the cost of the repair into the price. Still running strong since 2003.

I had done a great deal of reading up on how to buy used tooling on rec.crafts.metalworking news group on usenet news as well as on the web. I didn't find this place till 2004 or so. I also own two other lathes, a Unimat SL and a late model (70's) Atlas 6" which helped me a bit as I wasn't totally unfamiliar with lathes. In general I was fortunate to find a good seller. I like to be able to look at what I'm buying in person. If the seller seems shady (like one used machinery dealer I talked to in Lemon Grove) I'd pass. The 8520 mill is also in well used but decent shape and I'm very happy with it. My Rotex horizontal mill wasn't in such good shape. Dirty, oily mess that had (has) issues with the Acme nuts and lead screws for knee as well as X & Y axis. Ways looked good though and the spindle seemed in good condition. Once I took it apart I found the spindle and bearings were in very good condition. I bought that because I was looking for a project machine. I still have to finish that project. I found the Rotex on Craigs list. I also found a set of machinist tools from a former machinist on Craigs list. I went to look at that and as soon as he opened up the drawers a started showing me the contents I knew I was going to buy as it was all in good condition but used. You could see he had taken care of his toys.

Expect some problems with old used machines. Get as familiar as you can with what you are trying to buy so read up on lathes and how they are used. The link posted by Fasttrack in the first post above will take you to some very useful articles on evaluating used machines. Note that at the end of his article he mentions he doesn't even take a dial indicator with him to evaluate a lathe. I read these notes many time before I began looking. All of this is based on a home hobbiest perspective if your equipping a business then your needs are different and should be addressed accordingly.