Lathe inspection tips

Next week I'm going to fly down to L.A. and look at the Mori Seiki there.

My googling has turned up http://www.mermac.com/advicenew.html which has tips on evaluating a used lathe, but I haven't found anything else like that, and my searches here haven't turned up more than the odd tip here and there.

Does anyone have other things I should watch for, especially when evaluating a lathe of the size and quality of the Mori Seiki 850?

thanks,
Michael

Michael: Tony's UK lathe site has some tips for buying a lathe.

Dave at Mermac says you can't take too much time examining it. I don't buy it (as an HSM) since I only planned on bring home ONE 1500 pound lathe in my lifetime (ok, maybe 2) ... and I do precision work.

You've gotta ask yourself several things also:

1) what are you going to make with it?
2) do you want precision when you flip the switch or are you prepared to rebuild (esp. grinding the ways, etc.)?
3) how much are you willing to pay and don't forget that tooling can easily exceed the price of a used machine

Here are a few points I've used and would suggest to give some feel of condition and precision:

1) listen to the machine in all speeds, one spindle bearing can cost $1500 or so on some machines (probably more on larger machines).

2) measure runout at the spindle nose and taper

3) indicate a flat, unworn tailstock way from the carriage while traversing up and down the ways (level of concern should be based on tolerances you need to hold, size of parts and whether or not wear is in the front V only or both front and rear are worn uniformly)

4) if cutting threads, examine the condition of the leadscrew, feel the halfnut engagement

5) examine the cross slide leadscrew

6) check the cross slide fit near the area it would be in for small diameters and then further out, noting difference in cross slide play and fit

7) this may be a bit much but if you plan on facing large parts ... check cross slide perpendicularity to spindle ... refer to the machinery rebuilder's book or indicate a parallel held in a 4 jaw, rotate 180 and adjust parallel for same reading at 0 and 180 degrees ... then indicate along the parallel from where the cutting tool would be about on the center line to about half the swing of the machine

8) general condition ... are oil levels all up, is the machine oily or one of those that served in desert duty ... any signs of grinding or abrasive slurry?

9) what power does it need and can you supply it?

10) tooling, rests, etc. that are proprietary and costly (especially gears)?

These comments are based on closely examining three or four machines in the 12" - 13" range, bringing one home, taking it back and finally, landing a very nice Harrison M300 recently

Den

Hi Den,

That tip on measuring the parallel in the chuck is one I hadn't seen before. I do foresee facing good-sized stuff now and then. I'll look at the lathes.co site - I don't think I'd noticed any tips there.

If I'm taking a day off and flying from SF to LA to look at it you can be sure I'm going to spend more than 5 minutes looking at it. It is at a dealer and he's not going to want to rush me if he thinks he can get me to make a major purchase. If I get this lathe (or one like it) I'm figuring I will be $10-11K out of pocket by the time it is delivered, tooled up, hooked to a bigger source of 3 phase than I currently have and running in the garage, and I'm not wanting to buy a pig in a poke.

Even with a one year warranty for parts I'd prefer to not have any need to use that warranty.

I think he said he's got another Mori there now, as well as Whacheons of similar size so I'm planning on having him power up 2-3 different lathes so I can compare them all to see what kind of noises they emit and what vibrations I can feel. He also has a blown-up Mori that is apart so I can look at the innards and get a feel for the quality of them.

I'm mainly concerned with evaluating the lathe rather than the tooling as that is the big part of the purchase. If the chucks don't seem to move smoothly, close evenly, and/or show signs of crashes/wear I'll have those swapped out or deducted from the total.

I'm sure the dealer will put the best spin on the lathes' conditions that he can - that's his job. I'm hoping that by starting with a lathe that began life as a rugged and high-quality expensive machine that it won't have been abused and will have held up better to the use it has gotten. But anything can be run into the ground if someone is willing to work hard enough at it.

I'd guess the Mori has hardened and ground ways so I may not be looking for scraping marks on them. It seems like a 4500 pound short bed (34") lathe should be pretty stiff, so I'm hoping that any force sufficient to have twisted the bed will have been big enough to leave major visible crunch marks on it.

It seems like it would be worth letting the lathe run for a few minutes at low spindle speeds to warm things up a bit in the head and transmission. I don't know if lathes are set up loose and things tighten up as they warm, or if they tend to loosen up as they get warm.

My preference would to be to have an independent lab run as a charity by a wealthy philanthropist do a full inspection on anything I buy, but that seems to be unlikely to happen.

cheers,
Michael

Warm up is a very good idea as it give the oil a chance to drip, pump or whatever on its way to the spindle bearings and gears.

Indicating a flat, un-worn tailstock way from the carriage will give an indication of wear in the carriage ways or the underside of the carriage itself. Of course, the late would need to be perfectly level for best results.

I had evaluated and brought home an Emco Super 11 last December which turned out to have an incredible 0.030" - 0.040" of wear under the carriage ways ... the V ways were more like several thousandths. After lugging it back to the dealer, it taught me to keep an eye open to the less than visible wear that can be present. The carriage had dropped so low that the pinion gear no longer had adequate contact with the rack

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[This message has been edited by dennh (edited 06-29-2004).]

I have run lathes for many years and by far the best test I found was to put a bar in the chuck and turn it then drill the end of it and thread it. Thats the utimate test.
Don

question. I was wondering if it is possible to reverse the hard steel way inserts on a LeBlond so the wear would be on the right end. I assume the insert channels must be precision machined because the hard inserts would not have been groudn after inserting. ANy experinece on this?

Donie

I think great advice, I would only add run it thru all speed ranges.

On a geared head lathe there are different gears in mesh for different speeds and you could miss a bad gear unless you checked all ranges. Same idea for the leadscrew quick change gearbox.

If you were super motivated you could do something like take a precision straightedge to the ways...this would eliminate gross way problems like Den mentioned and might be appropriate for a short bed lathe like that.

You could also cut and mic a test bar, really that only checks headstock-tailstock alignment but you could see if the previous owner/user had them dialed in.

Any operations involving actual metal cutting would require a minimum set of tooling...maybe a good idea to ask the dealer about this ahead of time so they could be prepared with some tooling???

As far as a crash twisting the lathe bed I would be a little surprised if plastic deformation could be done to this casting without a fracture but then again I'm surprised every day. Knocking the headstock out of alignment with the ways after a crash might be a more probable failure mode.

It all is very interesting.

-Matt

C'mon Donie: After all those informative posts in the other forum about testing lathe accuracy down to a gnat's ass hair, this is ALL you're gonna do
Den

dennh, I first started as a machinist in the mining and logging industry in the 1970s. Most of the equipment in the shops then was coverted line shaft machines. To do reasonable work on them, you had to feel out each machine and try to find a sweet spot, that is usually the ways were so worn out near the chuck that you had keep the carriage back on a less worn area of the bed and somehow extend a tool forward.
One of the worst lathes I ever used was a Roth 20 x 80, it was so worn that I had to use a left hand boring bar extended about 12" to turn the OD on a short piece in the chuck. Sounds pretty dreadfull but I learned that reasonably good results can be had from the worst equipment.
In the 80s the Forest Service and BLM mandated that equipment used on the public lands could no longer puke oil all over. I stayed buisy making or modifying hydraulic pistons using Parker Polypak seals. This exposed me to close tolerance work. I then began working in hydraulic shops and rebuilding pumps with rotating piston groups.
Because of this experience I was lured away by a Harley Davidson factory representive to work at a new dealership to get it off the ground. I took it on the condition that I would be certified at Milwaulkee and a new bike.
I missed the machine work and went back to it after 3yrs.
I was able to get in a job situation that required the most extreme precision on very expensive work using the best of equipment.
To get the best results out of the best equipment I had to use many of the old tricks that I had learned on the worn out equipment.
Here is what I do to set up my Monarch EE lathes. I take a true tested shaft extend it only 5" from an ajustable chuck, true the shaft at the chuck and 5" out to better than .0001. Put an indicator in the tool post and move the carriage back and forth along the 5" bar length. Now this is when I adjust such things as carriage gibs. Also this will show the good and bad on the ways. If you dont like the way the head stock is pointing, try loosening the bolts that hold it to the machine and push on the headstock the way you want it to go and retighten the bolts indicate the test bar for improvement. Some fine tuning can had by vary the tourq on the bolts.
Now more of that Wild Turkey!
Don Dyar

"To get the best results out of the best equipment I had to use many of the old tricks that I had learned on the worn out equipment"

A good point to remember from this ... there are no free rides and a Hardinge, Monarch, etc. is not going to turn one into a precision machinist overnight.

Your comments on rotating the headstock got me thinking about tests for cross slide perpendicularity. I've adjusted several small machine headstocks but on my Harrison M300, never questioned the validity of the cross slide perpendicularity test ... a parallel, held in a 4 jaw, rotated 180 and indicated for same reading at both ends, then indicated along half its length. I just realized that this test has got to follow a test for headstock alignment to the ways otherwise it proves nothing ... doh

I've got about 0.001" taper in 7" turning a 2" 6061 test bar and the cross slide is off about 0.0015 over its travel. If I tweak the headstock, the cross slide should come back to about normal (intentional, slight concave cut).

Den

Yes the headstock must be true to the bedways for OD and ID turning. If facing cuts are ending up a little convex, all that can be done is scrape the crosslide.
Facing cuts are best a little concave, because it makes a better pressure seal like on flanges.
On my best Monarch EE, I can not hold better than .001 for taper in a couple of inches using insert tooling on a work piece only held in a chuck, I have to use an AR style bit that is machine sharpend with a very small nose radius, less than .001 feed about .00075 depth of cut and high spindle speed. On chrome alloy tool and machinery tpe steels.
I would use caution about fiddling with headstock alighnment when the problem is tool and work deflection.
Don

The 2" aluminum test bar I used was cut with a small radius insert at slow feed. The 0.001" taper across 7" was with the bar held only by the chuck.

I've often thought about the relevance of these specs when all parts deflect to some extent and when between centers, the tailstock is adjustable. And, deflection must be exacerbated by negative inserts big time, right??

I guess concave is or was desirable. The Harrison test sheet calls out a 0.0005" limit (concave only) across a 12" faceplate (I'm assuming only center outward).