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dahui · #5 02-13-2007, 04:55 PM

I'm new as well, but here are some things I have tested on my ST. Let me know if you need more procedural details. And yes, DRO is the way to go.

1) Check the backlash on all axes. I wrote them on my DRO screen with a silver sharpie. When I measure, my repeatability is will within .001, but when I'm making parts sometimes I end up scratching my head. As in, measure OD of a turned part, set DRO, take a few cuts, measure...and my DRO is off by a few thou.

2) Check/set the angle of the table perpendicular to the X axis.

3) Check the alignment of your tailstock (center, height, and parallelism to the ways)

4) use a 4 jaw chuck and dial indicator for turning. However, my three jaw seems to be more accurate that I would expect.

5) check the runout on the lathe and mill spindles. I found the 3/8 collet that came with my machine was junk. Buy some high quality collets. Remember, accuracy (or inaccuracy) is a compounding problem. You will only be as accurate as the least accurate part of your setup.

6) Also, make sure the mill spindle is perpendicular to the table. I'm not sure of any way to adjust that if it is in fact out of tram.

7) Adjust the gibs on the X and Y axis. I had to make a new gib for the X axis to get it to adjust correctly. The gib that came on my machine was signifcantly warped and I couldn't adjust out the play without getting a really sticky travel.

8) On that note, watch out for the table rotating around the Z axis when you move the X axis...adjusting the gib should minimize this. However, when I'm turning I try to set the Y axis travel at zero and set up the tip of my turning tool to be over the center. This should minimize the effect of any rocking that does occur.

Oh by the way it would be good to know if you are using CNC and what particular operation you are having trouble with. If you are not using CNC and have acme screws, it's also very important to set your position when traversing the axis in the same direction you did when you zeroed out...otherwise you will be off by the amount of backlash.