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Pherdie
03-11-2009, 06:43 PM
The scenario:

Lathe is a Jet GHB-1340A, 13 X 40, which sits on a sheet metal cabinet. The lathe/cabinet was leveled out when received and sits on a concrete surface. The cabinet portion supporting the headstock end has four adjustable rubber bottom machine mounts, the tailstock cabinet end has two. The 2" diameter rubber machine mounts (my add on many moons ago), equipped with 1/2-13 studs, can rock like a drunken sailor in a high wind when the lathe is physically pushed. I recently added a VFD and changed the motor to a Leeson, which is MUCH heavier than the original motor. The motor hangs on the backside of the bed, under the headstock (lots more weight torquing the bed and compressing the rubber mounts). My level is a Russian machinists level purchased through Enco and rated at "0,10" (.10?) mm/m. It was compared to a $1K Starrett I was loaned and appeared to be dead nuts as compared to the Starrett (pleasantly surprised!).

A recent project requiring high accuracy pointed out that my lathe is now highly out of alignment. Although I was able to compensate for the purposes of the project, I now want to resolve the alignment issue, which has me asking the following questions:

1) In the interest of accuracy and repeatability should the rubber mounts be removed and replaced by some other 'solid' hardware, so there is metal to concrete contact for maximum rigidity?. Am I getting too concerned about this as the lathe is sitting on a flimsy sheet metal cabinet anyway?

2) What is the proper procedure for leveling out a six point mounting system like mine? I have retracted the inside support mounts under the headstock cabinet to start with, then leveled out the outer headstock cabinet support mounts fore and aft (straddling the bed near the headstock), then leveled the tailstock cabinet supports, fore and aft (straddling the bed near the tailstock) then leveled the bed lengthwise by adjusting the tailstock end cabinet supports in unison and finally level the chuck as referenced to the length of the lathe bed by adjusting the two inside headstock cabinet supports. Right, wrong?

3) How often should lathe alignment be checked??

4) Any other guidance?

Thanks in advance,

Fred

lane
03-11-2009, 08:17 PM
Sounds good to me . Mine is similar . But get rid of the rubber feet . Get it down on solid floor. I tried that rubber process once lathe that size not heavy enough to work . The cabinets are too light duty.Not enough weight down low. I double check mine every now and then. and always a few weeks after leveling because it will settle.

japcas
03-11-2009, 08:38 PM
I agree with Lane. Get rid of the rubber mounts. I have the same lathe but I used the solid metal adjustable feet with the ball sockets on the feet. Ordered them from Enco. I haven't checked mine since I set it up but it doesn't rock any. It seems to be as accurate as when I set up so I haven't bothered with it any. Good luck.

wtrueman
03-11-2009, 08:46 PM
I had two new Lantaine lathes and had to set 1/2 inch steel plates into the cement to get the firmness I wanted. They have worked well for 29 years. If your machine is the slightest bit top heavy, consider welding anchor chains to the steel in the floor and then bolting the chain to the lathe. This worked for me and about 500 grade 9-12 shop kids. my .02$, Wayne

ahidley
03-12-2009, 09:05 AM
It does NOT matter if the lathe is level or not. It matters if the spindle is square with the ways and the tailstock is square and on center with the spindle. A ridgid/solid machine frame is important also to prevent flex. If its mounted on rubber feet then the frame MUST be ridgid/solid because the concrete on the floor does NOT do crap.

Carld
03-12-2009, 10:40 AM
Get rid of the rubber pads and put it on metal pads with a drilled recess for the leveling bolts. Sometimes you even have to anchor it to the floor to remove a twist in the bed.

Pherdie
03-12-2009, 04:35 PM
OK, per consensus of the group, the rubber mounts have been removed. I went with some inverted 1/2" bolts, but the 1 1/2" bolt shoulder limitation put the cabinet/lathe higher in the air and made it very unsteady. This defeated my ability to be able to not only keep the system low, but to have room for a large washer and locking nut, top and bottom with reference to the cabinet base adjustment threads, in order to improve stability.

I whizzed down to HD for some fully threaded bolts, but in anything over 2" in length, there was a shoulder. Then went to Orchard Supply and found all sorts of full length threaded bolts. Went with some carriage bolts and I'm installing them now.

It's kind of amazing how "level" varies along the bed length. The ways can be perfectly level (lengthwise) at the tailstock and considerably off at the headstock. Apparently the cast iron bed is far more dynamic than I ever realized. Maybe after a 100 years the bed will slump like an old glass window pane :D !!