Large lathe levelling

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earlgo
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Re: Large lathe levelling

Post by earlgo » Tue Nov 07, 2017 10:06 am

Weedy64 wrote:The floor is certainly not flat.. but so far the 3/4 plate just conforms to the floor with weight on the jacks-screws.
This is the reason for the heavy felt that is put down between the plate and concrete. I think some of the felt I saw was tarred and it reminded me of the black sheathing that used to be used for house construction. It was also about 3/8" to 1/2" thick.
--earlgo
Deja Poo - The feeling you have seen all this crap before.

Weedy64
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Re: Large lathe levelling

Post by Weedy64 » Tue Nov 07, 2017 10:59 am

20171106_160223_resized.jpg
1966 Monarch 612 25x144 19over saddle 16k#

about to lift tailstock, to repair clamp, vermin patrol in the sunlight
20171106_160309_resized.jpg
sight glass oil leak :| headstock is solvent washed, yeah the rest is as dirty as it looks

update: bed level within .002 long, .0005 across before I went to bed. Will let it sit for a few days and recheck it before I try a cut or two

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neanderman
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Re: Large lathe levelling

Post by neanderman » Thu Nov 09, 2017 12:54 am

earlgo wrote:I think some of the felt I saw was tarred and it reminded me of the black sheathing that used to be used for house construction.
What became of that stuff? I think it was also used for expansion joints in sidewalks.
Ed

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pete
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Re: Large lathe levelling

Post by pete » Thu Nov 16, 2017 6:40 pm

Fwiw I just watched Tom Liptons lathe leveling video on his Oxtools Youtube channel last night. I think it's just what your looking for Weedy. Properly aligning and testing a machine tool is a far more complex topic to understand than it first seems. In 1927 Dr. Georg Schlesinger pretty much wrote the book on testing machine tools. I think his work is now up to about the 7th edition but doing a Google search will pull up at least a couple of websites that have PDF's of his testing methods that should be helpful as well. My previous trial and error efforts until I learned what works on smaller lathes sure seems to agree with everything Tom Lipton mentions with his larger lathe. But basicaly you start with the headstock end and get that leveled across the ways, then get the bedways leveled from the tailstocks end in the longitudinal direction with the headstocks end. Then level the cross direction at the tailstock end. Once all the support feet are taking the weight you then double check all measurements to make sure nothings shifted. Only then do you align the tailstocks spindle to center it with the headstocks spindle cener line. Even with the machine as perfectly level as you can get it I've found some minor adjusting is still required after making test cuts. On a larger lathe it's tiring, can take a fair amount of time and a bit frustrating with all the up and down making adjustments until the whole machine is level and bearing equally on the support feet. Tom had to adjust his headstock casting but that would be the very last thing I'd touch unless I was 100% positive it was out and it's not something else.

Checking for any taper is done with test cuts as Tom shows. I still leave the headstock end alone since it's the most rigid area and adjust that taper out using the center and tailstock support feet. If your test cuts show small at the tailstock end you come up on the rear supports and down on the front. If large at the tailstock end then just the opposite. It's easiest to metaly visualize it as your trying to roll the shaft towards or away from the tool tip until you get a parallel cut.

Weedy64
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Re: Large lathe levelling

Post by Weedy64 » Mon Nov 20, 2017 12:00 pm

Took the plates out and am starting again. :(
The steel plates where too thick and were providing springyness, I was close when using 8/12 bolts but chasing my tail after that. and I think the headstock and tailstock adjust. bolts were swapped, I easily ran out of bolt on the headstock. They are same thread but the one set are longer with full size jam nuts.

Weedy64
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Re: Large lathe levelling

Post by Weedy64 » Wed Nov 22, 2017 5:56 pm

It seems to be holding level now, in direct contact with the concrete floor with no steel plates flexing with load, and its that much lower to the floor, Im not 6'4" 8)

I used T. Liptons trick of putting the tail pedestal on a single point (stub shaft parallel w. ways) and leveled from headstock, mid-bases and then tail-base and removed stub shaft as tail-bases adjusters took the weight. The adjusters seemed much less interactive than before when the tail was not on a single point or maybe it was the flexing plates. Will let er sit for a bit and see if I get any drift.

I cleaned up the tail-stock and found an oil port for one side of the V was blocked, had to use an 6"long 1/8" drill, a pokey wire wouldn't do it, a chip or casting slag was in the way. I fixed the abused/cracked quick clamp. Takes a lot of solvent to clean the residue off all those parts.

I think I should lift off the top of the carriage and make sure its oil ports are open, and Z reliefs are clean, its been sitting too long. Trouble is everything is crane removal time, its big for one person.

There is an oil pump in the apron with a filter but I'm not sure how it functions but I know there is a filter inside the sump, so Ill start with that.

Weedy64
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Re: Large lathe levelling

Post by Weedy64 » Tue Dec 12, 2017 12:21 pm

Well, the bed is not twisting. Its within 5/10s just some belly in the middle so I think I will back off the two end pairs of adjusters and put some more down force on the adjusters of the two pedestals supporting the middle of the lathe. I cleaned the apron sump, yuck, washed the oil pump screens and filters and refreshed the oil and it appears to oil the ways so the pump and tubings are working, Re-re the cross and compound dials n hand-wheels - they feel nice .003 bkl. I think I can put off lifting the carriage and taper system, I need to make some paying chips for a bit. Ill get to it in the summer when I have less jobs waiting.

I had re-re d the gearbox and siliconed the sump on it but it leaks I tightened all the +20 screws and i guess squeezed all the sealant out....rookie. On the apron I hand tightened the sump and sucked up the screws much later....it doesn't leak. Lesson learned if I can remember it. :P

pete
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Re: Large lathe levelling

Post by pete » Tue Dec 12, 2017 7:05 pm

Have you run a turning test under actual cutting conditions? I've found even with a lathe mounted to a 1" thick steel plate and being leveled as true as possible with a very accurate level I still had to do a very small amount of tweaking to the mounting bolts to bring it in as parrallel as possible. Those are some great backlash numbers. My mill when brand new had .004"

Good tip about hand tightening the bolts and waiting until the silicone cures a bit before final tightening. I need to remember that one.

John Hasler
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Re: Large lathe levelling

Post by John Hasler » Tue Dec 12, 2017 8:45 pm

Weedy64 writes:
> I had re-re d the gearbox and siliconed the sump on it but it leaks I tightened all the +20 screws and i guess squeezed all the sealant out....rookie.
> On the apron I hand tightened the sump and sucked up the screws much later....it doesn't leak. Lesson learned if I can remember it. :P

After many similar experiences (not to mention plugging an engine oil pickup...) I learned to apply minimal silicone to both parts and then let it set up before assembling. Under pressure the stuff will deform to fill gaps but you do *not* want it to flow.

I usually just use gaskets, though.

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neanderman
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Re: Large lathe levelling

Post by neanderman » Tue Dec 12, 2017 9:11 pm

For the Dual Drive QC box, I used some gasket paper from McMaster's and "Indian Head" shellac-based gasket sealer.

For the covers, I used neoprene.
Ed

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neanderman
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Re: Large lathe levelling

Post by neanderman » Wed Dec 13, 2017 1:51 am

GlennW wrote:I made this to check my lathe bed.
I'm quite intrigued by this, but how do you rule out error in your device; i.e., how do you know that your device is parallel to the bearing surfaces of the lathe bed?
Ed

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GlennW
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Re: Large lathe levelling

Post by GlennW » Wed Dec 13, 2017 7:46 am

You are using relative readings to eliminate twist in the bed.

The bed itself does not have to be dead level to within tenths on the X axis, just co planar.

Hardinge made slant bed lathes for years.
Glenn

Operating machines is perfectly safe......until you forget how dangerous it really is!

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