Tramming LMS 3960 Mini-Mill Help

[MaverickNH]

Here's what I've been doing:

I was seeing about 0.007 difference when just rotating a Dial Test Indicator on the spindle from the left side of he table to right. I took the head off the column and column off base, cleaned well (lots of grime and paint overspray) and reassembled. About the same 0.007 difference, so I started looking into table flatness and spindle-column alignment before doing any shimming.

1. I Laid a Surface Plate over the table - no greater than 0.002 feeler can slip under however I rotate plate and slide it around - might be my cheap technical plate rather than the table.

2. I Clamped a Starrett Toolmakers Square (6') to left and right sides of table, 2nd and 3rd ribs of table, and ran a Dial Test Indicator up and down the 6" side. On right of table deviation is 0.0015 but on left it's 0.005. Same measures on 2nd or 3rd ribs, checked each side twice with same outcomes. The square is certified square to 0.0002 along the 6" length.

This suggests some spindle-column alignment issue, but why biased on one side 0.005 and only 0.0015 on the other?

 

[Richard King]

It sounds like the table has a twist in it. I would mic the table thickness. 4 corners and middle . The table should be the same thickness with in .001".

Next put drill chuck in the spindle and mount your indicator in the chuck and lower the head and indicate the top of the table side to side in front, middle and back. This should also be with-in .001. Do that and let me know what you get.

Here's what I've been doing:

I was seeing about 0.007 difference when just rotating a Dial Test Indicator on the spindle from the left side of he table to right. I took the head off the column and column off base, cleaned well (lots of grime and paint overspray) and reassembled. About the same 0.007 difference, so I started looking into table flatness and spindle-column alignment before doing any shimming.

1. I Laid a Surface Plate over the table - no greater than 0.002 feeler can slip under however I rotate plate and slide it around - might be my cheap technical plate rather than the table.

2. I Clamped a Starrett Toolmakers Square (6') to left and right sides of table, 2nd and 3rd ribs of table, and ran a Dial Test Indicator up and down the 6" side. On right of table deviation is 0.0015 but on left it's 0.005. Same measures on 2nd or 3rd ribs, checked each side twice with same outcomes. The square is certified square to 0.0002 along the 6" length.

This suggests some spindle-column alignment issue, but why biased on one side 0.005 and only 0.0015 on the other?