Tramming my HiTorque 3960 Mini Mill

[MaverickNH]

I mounted my new HiTorque 3960 Mini Mill to the work bench and did some measures to assess column trueness to the table. It looks to be +/- 0.001 in the x-axis by the y-axis is 0.005-0.007 low toward the column (that is, higher in the front, lower in the back).

The x and y axis gibs seem well adjusted, and I snugged the column bolts to be sure they were not loose.

Never having corrected tram in a mill before, I thought I would check my plan with those that know more.

I have some brass shim stock in thicknesses 0.001, 0.0015, 0.002, 0.003, ..., 0.010, 0.012, 0.015 on hand, so rather than use foil or a beer can, I figure to shim the front of the column up using the brass. Maybe add 0.003 left and right and re-check.

Sound right?

 

[OakRidgeGuy]

That is where I would start! I have been playing around with mine a bit, but I will have to do the same thing.. I need to put a .002 shim under the right side of column.

 

[MaverickNH]

So I picked up one of those Pro Tram Mini dual indicators like the below. It has a 3 inch space between indicator tips. I can shim the X and Y within 0.001-0.002 with the table centered.

When I crank the table from all the way left to all the way right, and all the way front to all the way back, it seems the variation is greater - up to 0.003.

What is good enough? I'm sure it depends on the precision required, but I'm wondering what to expect on a Mini-Mill for under $1000.

 

[DMS]

Tramming these little guys the first time can be a bit involved the first time, but it will make a great deal of difference. The first thing to do is to pull the head of and make sure there is no paint stuck in the dovetails. This can cause all kinds of "interesting behavior". Then you want to make sure the spindle is parallel with the column. I did this by putting a piece of drill rod in a collet, then mounting a dial indicator to the column, and putting the indicator on the drill rod. Run the head up and down. If it's too far off you can add shims to adjust. The head is actually 2 pieces, though it is hard to see through the paint. I scored along the seam to try to minimize damage to the paint, then loosened the bolts on the back of the head (you need to remove head again to do this). Add shimstock between the two halves and re-tighten. Then, measure again.

It seems like a pain, but it really doesn't take too long. I also found it easier to remove the column from the base and lay it flat on a bench while doing this.

Once you have the spindle parallel with the column, you can tram the head to the table. for that part, you've got the right idea. For really small shimstock, aluminum foil works great, but start with the brass and get as close as you can.