Tramming - what is acceptable?

Decided to check my mill this afternoon -it's a circular column Warco 'Economy' mill/drill.

It was not too far out, measured on the table in four corners roughly approximately equal to the spacing of the four holding down bolts I got readings from 0.000 at the start reference to +0.003" max. Shims steel available is 0.001, 0.003, 0.004 and 0.006 thou.

After a couple of hours adding and taking away shims I now have from my 0.000 start reference back left, to -0.0015 front left, -0.0015 front right to -0.001" back right. I could live with that, but feel it could be better.

Question: What is the acceptable error on Tramming, can I expect to get it better on this sort of mill?

Chris

Edited By ChrisH on 16/02/2014 18:03:32

Chris,

It depends on the distance of your indicator from the spindle axis. Those distances you've quoted over a 3 inch radius would keep me happy.

HTH

Rod

Hi Rod,

Just been out to the shed to measure the radius, from the spindle axis to the indicator - it's a 4 inch radius, so presumable that is a good result but I can't help feeling it should be better.

I will leave it until tomorrow and recheck, see if it holds at that.

Chris

I would say that is pretty good, I have spent many happy hours 'tramming' turret mills and if I got it within a thou over 4" I would be good to go. On a knee type of mill you can have perfect squareness quill to table but still have faint steps in the work face due I believe to the table being out of square to the column movement?

Tony

Oh Michael, now you have introduced a whole new bag of worms!

How do you determine if the column is crooked and/or the spindle/quill is crooked, and if any of them are, how do you correct other than by renewing? Other than by Tramming the column to the table that is.

Chris

As far as tramming is concerned, assuming that the head moves in straight line on the column, I don't think it matters if the column isn't perpendicular to the table. If the spindle is trammed to the table it stays trammed. The spindle will move in X and/or Y as Z changes, but that's a separate issue.

Andrew