Getting twist of of lathe with only 2 mounting points

GunsOfNavarone

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I was going to post this under Grizzly, but there are so many clones, others have dealt with this hurdle.
So my table i have my lathe to is substantial, I believe it holds 2k lbs...2 inch butcherblock, heavy steel legs that are braced. I have the table level with a machinist level and the top surface is true/smooth.
The lathe (Griz G0602) is bolted down via 2 mounting bolts at either end of lathe, running under direct center of lathe. They are just lightly tighten, no more. !!!!¡¡¡¡When cutting the rest shape (barbell) out of 6061, the tailstock end is +.004 bigger than spindle end.¡¡¡¡¡!!!! I believe that means the fix is lifting tailstock side/front. *I did level the lathe with machinist level as well* There really isn't a way to do this, again there is only one mounting point and it is under the centerline. Also, this is not being cut with any assistance of the tailstock....this is chucked only.
From the factory, the readings are;
Parallelism of tailstock to longitude motion in
Vertical plane .026
Horizontal plane .028
Spindle can action .018
Spindle nose run out .0175
Spindle taper run out at
Nose test bar .018
End test bar .0285
Parallelism of spindle centerline to longitude motion of carriage
In vertical plane .0485
In horizontal plane .027
Difference in center height between headstock and tailstock .058
I assume these are metric readings, and they are more, but n case there were follow up questions...
 
Oxtool has a video on leveling a lathe--which is about removing the twist in the rails not getting the lathe perpendicular with respect to the center of the earth.

I leveled my lathe using a level (duh) and a torque wrench to make sure all 8 machine pads were holding the same load.
 
Yeah. I watched his video a couple weeks ago, but having 8 adjustable legs versus none, I'm kinda at a dead end..changing my tables level has no bearing on the lathe mounted to a 2" thick table top, twist. Hmmmm..if be better taking a torch to the ways, but I won't do that!
 
Can you shim up one side of the lathe between the table top and lathe base?
 
It's not the greatest picture, but there really is just a center pod, only about 3" wide. Doesn't really seem as if it will have the ability to counter the twist. I guess I can find with it, such a nightmare to level again if it doesn't help. I'm sure someone else has had to do this on a Chinese mini lathe.

2018-07-28_11-36-29_371.jpg
 
I just did my G0752. I made levelers from 1/2" plate with leveling bolts. Mounted 1/4" plate on the bottom of the feet. Very simple to get the bed perfectly parallel with this system. I'll make a step by step post later today but here's a preview...









 
Interesting, having some adjustable feet would be glorious! I’d be interested how it all connects at bottom. These 4 adjustable bolts are not connected in any way to bottom of lathe? What is the raw steel bar running along bottom of lathe in 2nd to last picture? I would guess you still have it (the lathe) bolted down to table top, this just extends that connection? I would guess a much simplified version would be to loosen my 2 mounting bolts and cram a shim under front right and crank it down on top of it...that would tweak the beds in essentially the same manner. I just installed this a couple weeks ago...seriously don’t want to start over. Yeah, any diagrams of detailed pictures would be great when I get around to starting from scratch again.
 
Interesting, having some adjustable feet would be glorious! I’d be interested how it all connects at bottom. These 4 adjustable bolts are not connected in any way to bottom of lathe? What is the raw steel bar running along bottom of lathe in 2nd to last picture? I would guess you still have it (the lathe) bolted down to table top, this just extends that connection? I would guess a much simplified version would be to loosen my 2 mounting bolts and cram a shim under front right and crank it down on top of it...that would tweak the beds in essentially the same manner. I just installed this a couple weeks ago...seriously don’t want to start over. Yeah, any diagrams of detailed pictures would be great when I get around to starting from scratch again.

The leveling bolts are not connected to the lathe bed. They bear on the 1/4" plate on the bottom of the feet. There is a 4 1/2" x 1/2" thru bolt going through the original mounting hole and extending all the way thru the bench top.

You can use shims to accomplish the same result but it will be a trial and error operation.

I'll make a detailed post later today.

 
Personally I would forget the level and just shim it until it stops cutting tapers. Once that's done level by using the table feet.

Sent from my H3123 using Tapatalk
 
I have the 602 lathe and face the same issues. I plan to put 5" x 7" x 7/8" steel risers under the feet. The primary reason for this is for better access to the lower motor mounts. As shipped it isn't possible to service the motor without lifting the lathe which will destroy any alignment. The additional clearance under the bed for cleanout will be nice too. Just need to get the tanks filled so I can make the rough cuts.

My stand is made from steel with a full width section of 7" channel running under the lathe and covered with a sheet metal skin. The risers will placed on top of the chip pan and bolted through to the channel and should provide a solid base for the lathe mount. Terry's alignment method would be a good addition.

My stand has leveling feet, using the same concept. The issue with them is they tend to walk on the floor when trying to make an adjustment. OK for rough adjustment but it sucks when trying to get those last few thousandths. I also have a typical four point alignment and have decided to go to three points for the stand. This will prevent twisting the stand and adding stresses which telegraph up to the lathe mount. The third alignment point will be under the tailstock and the original corner feet on the right end will be adjusted for light contact to prevent any rocking of the stand.
 
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