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johnvi
03-04-2009, 04:59 AM
The table on my mill changes in height when traversing, and I would be grateful for some advice how to isolate the problem and fix it.
It is a King Rich Mill (Taiwanese Bridgeport copy), in otherwise excellent condition. The indicated height difference of the table end to end as it passes under the spindle is about 0.1mm.
The machine has been levelled accurately. The gibs are snug but not too tight. There seems to be minimal wear on the table surface.
The original documentation records the parallelism of the longitudinal movement of the table top at 0.012mm which is 1/8th of what I am measuring now.
Suggestions??

oldtiffie
03-04-2009, 05:36 AM
Measure the distance from the top of the table to the underside of it (where the "X" slide is) - at several places. If they are all reasonable, I would think that it might be:
- wear in the table component of the "X" slide;
- wear in the apron component of the "X" slide (at the ends);
- wear in the "Y" slide (apron or knee);
- table tilting as it approaches "out of balance" state at end of "X" traverse. This can be caused by either having a vise or a rotary table in the table during the test or the result of leaving one mounted pretty well permanently at the end of the table as a long-term basis causing uneven wear. It can be caused by wear of "slackness" in the "Y" gib; or
- wear in the vertical vee-ways on the knee and mill main body.

I'd suspect and check and if necessary re-adjust all gibs.

derekm
03-04-2009, 06:20 AM
Measure the distance from the top of the table to the underside of it (where the "X" slide is) - at several places. If they are all reasonable, I would think that it might be:
- wear in the table component of the "X" slide;
- wear in the apron component of the "X" slide (at the ends);
- wear in the "Y" slide (apron or knee);
- table tilting as it approaches "out of balance" state at end of "X" traverse. This can be caused by either having a vise or a rotary table in the table during the test or the result of leaving one mounted pretty well permanently at the end of the table as a long-term basis causing uneven wear. It can be caused by wear of "slackness" in the "Y" gib; or
- wear in the vertical vee-ways on the knee and mill main body.

I'd suspect and check and if necessary re-adjust all gibs.

Make sure you are doing the measurements with the knee(z) and Y locked firmly to eliminate some of the components of the last few of tiffies suggestions...

you can also mount a dial gauge/s from the column to the knee and from knee the to saddle to check for movement as you traverse the table.

you should also check the saddle to table for movement by attaching a dial gauge to the saddle to measure on the table surface

Derek

johnvi
03-04-2009, 07:53 AM
Thanks oldtiffie and Derek. Very helpful and logical suggestions. I will post results for your interest in a day or so.