Tramming questions

[westerner]

One trick in tramming is to mark points on the table centered on the quill that correspond to the spacing of the 4 bolts that hold the column to the base.

This trick right here will save DAYS of fiddling around. If you can actually measure the exact departure from square, then your shimming questions are answered from the start.

 

[graham-xrf]

This trick right here will save DAYS of fiddling around. If you can actually measure the exact departure from square, then your shimming questions are answered from the start.

Jim is right!
Use every trick there is because the practical business of making adjustments by shimming takes a whole lot of back-and-forth.
Once you have the right shim, or combination of shims, it's great, but on the way, to find that when tightened, a shim is not quite enough, or too much, is a frustrating drag.

Do not fear shims and shim material. The aluminium rescued from a drinks can is remarkably constant. Small adjustments can be made with foil, which comes in 35 micron, and I think the thicker one is double that.

One can get steel shim stock almost anywhere. McMaster Carr surely.
Or Amazon --> HERE
There is a more expensive type which comes as about 0.1" of many stuck together. You peel off as many as you need to get to the spacer you need. I am not so sure of that stuff as a way to go, but I have encountered it before being used to level a big tracking head.

It's best if you can use a single correct shim at a place needed, but you can as necessary contrive a 2-shim combination, or get creative with subtraction. e.g. if you dont happen to have a 0.002", but you do have a 0.003" and a 0.005", you can use the 5 and put the 3 on the other places. Not ideal, but it works.

You can get to any value you need in two shims with a combination of 1, 2, 2, 5, but the usual "set normally has enough combinations to get you there.

 

[Shotgun]

It's best if you can use a single correct shim at a place needed, but you can as necessary contrive a 2-shim combination, or get creative with subtraction. e.g. if you dont happen to have a 0.002", but you do have a 0.003" and a 0.005", you can use the 5 and put the 3 on the other places. Not ideal, but it works.

Or. . .
You can stop off at any auto parts store you pass while you're out and grab a set of feeler gauges for $5. For me, that was worth not having to fiddle with soda cans or counting layers of aluminum foil. I have a compartment in one of my parts bins dedicated to cut-off feeler gauges. Each leaf will render you two shims, and they have the thickness marked right there on them.

Combine this with the method of duplicating the hold down bolt pattern on your table, and tramming becomes a breeze. The only other thing you want to know is to use a torque wrench to torque the bolts in the same sequence each time you try.

1- duplicate the bolt pattern on the table, then mark the deviations from the highest spots. Write the numbers directly on the table. These are the shim thicknesses needed at those bolt locations.
2 - loosen all four bolts, push on the head to open up a crack, and slip the shims in, sliding them tight up against the bolts. It doesn't take much to tilt the head. If you need slightly more than the nominal thickness of the shim, slip it to the inside of the bolt. To the outside if slightly less.
3 - pick a pattern and a torque progression. I chose to tighten the bolts to 60ft-lbs, going clockwise, in 20ft-lb increments. The method isn't very important. Using it every time is.
4 - repeat until you're happy with the results. If a face cut gives you a herring bone pattern, you're done.

Take it from a guy that spent a week trying to get it right without success, and then getting it done right in less than an hour once I learned this process.

 

[raferguson]

Thanks everyone for their tips. I put two beer can shims on the right front, one on left front, and one on right rear. It was perfect until I got out the torque wrench. After torquing, it is still perfect left to right, but off .003 front to back. I measured my aluminum foil, three layers are .003, so I have my .001 shims. I can get it dialed in from here, take out two of the beer can shims and replace with two thicknesses of aluminum foil. By far the most time consuming thing was to make the jig, but now the jig is complete, and adjustable if I need to use it on a different machine. Thanks again.

 

[Christianstark]

Interesting strategy. I am assuming the results are more straightforward when the center of the bolt pattern on the table are equidistant from the column, as the center of the bolt pattern on the column are from the height of the table?

Edit - I guess it won't matter once everything is trammed, but I assume shimming becomes more predictable if it is a 1 for 1 ratio?

 

[Shotgun]

Interesting strategy. I am assuming the results are more straightforward when the center of the bolt pattern on the table are equidistant from the column, as the center of the bolt pattern on the column are from the height of the table?

Edit - I guess it won't matter once everything is trammed, but I assume shimming becomes more predictable if it is a 1 for 1 ratio?

Not just more predictable. The readings you get at each corner is exactly what you need at each corresponding bolt.

If the column were .001" too low at left rear corner, the dial indicator will read exactly .001" lower at that point on the table.