Greetings. I posted this elsewhere but I thought it might be easier to find here. I had to tram my LMS 3960 Mini Mill twice &, even using only one indicator, here's how I quickly got I got the 4-bolt column trammed really close.
I trammed the column last spring but, since I removed it to simplify installing the DRO scales, I had to tram it again. Last spring I made up a simple mount for the indicator & had decent results [within 0.002 in. over about 4 in of table travel]. This time I wanted to get it nearly perfect so I studied & followed the instructions in the manual &, to my surprise [at first], I overcorrected the error. The manual said to center the table under the spindle & take readings as far from the spindle as possible. I made an indicator mount that reached the 4 corners of the table & immediately found an error from the highest to the lowest corners of about 0.045 in. which seemed pretty high. I shimmed the corner with the highest deviation from "0" 0.045 in. & was surprised to find it even further off & in the opposite direction! After pondering this I found that increasing the distance between indication points to a distance that's greater than the column mounting bolt pattern magnified the error & that adding the shim thickness obtained this way grossly overcorrects the error. Bottom line: measure the spacing between the column mounting bolts & sweep the table [using parallels or smooth 1-2-3 blocks to avoid slots in the table] in a pattern the same size as the mounting bolt pattern & as closely as possible to the actual bolt pattern center. After measuring it this way I shimmed it again &, after tightening the bolts, the runout was 0.0005 in. within the pattern space &, from one corner of the table to the other, I had about 0.002 in. Hope this is helpful.
