Ussing shims to tram a X2 mill

[Zoltan]

My mini mill has the LMS solid column and base, where the column is attached to the base via bolts at the four corners.


I use shims between the column and base at the four mounting bolts in order to align the column. I'm currently using feeler gauges as shims. They are 0.5" wide and I always use two of them side by side to provide more coverage of the column/base mating area. Even so, the shims are only covering about 2/3 of the mating area.


So, once it's correctly trammed, should I buy shim stock in the correct thickness and make shims which would provide 100% coverage, or are the current shims adequate?

 

[Don B]

My mini mill has the LMS solid column and base, where the column is attached to the base via bolts at the four corners.


I use shims between the column and base at the four mounting bolts in order to align the column. I'm currently using feeler gauges as shims. They are 0.5" wide and I always use two of them side by side to provide more coverage of the column/base mating area. Even so, the shims are only covering about 2/3 of the mating area.


So, once it's correctly trammed, should I buy shim stock in the correct thickness and make shims which would provide 100% coverage, or are the current shims adequate?

I'm not specifically familiar with your mill, but I did have a mill with the same issues, and I really didn't like the thought of the column only having small contact areas after shimming, it was a Craftex mill, my problem was with the intermediate piece that went between the X Y table and the column, I removed the head and indicated the intermediate piece in relationship to the X Y table it was out (really far out, seriously a monkey with a chisel could have gotten it closer), I mounted the head to the X Y table and indicated (tested it's relationship to the milling table) and the head was good, I mounted the head to the X Y table facing backwards and used that setup to mill the intermediate piece, I'm not sure if this is an option for you it's just how I eliminated the need for shims:thinking:.

 

[chips&more]

I can understand your concern. Using shims leaves you with less than the 100% contact at the connection. Scraping and or re-machining is one option. I think I would first try an epoxy based filler like, Hysol Liquid Shim. I used the stuff on a mag base drill press column. I was in a hurry and this was a fast fix and thought I would be soon fixing it again. I was wrong, since the repair, it has held up very well through rigorous handling…Good Luck.

http://www.skygeek.com/henkel-hysol...aign=froogle&gclid=CKLr5fKxkL8CFRBhfgodX3MAMQ

 

[cazclocker]

Perhaps this thread should be moved to the "Little Machine Shop" section...???

I also have the LMS 3900 mini-mill, and I've trammed my mill with shims. I ordered an assortment of shim stock where each sheet measures 5"x9", plenty of material to cut any shape. I cut mine to 1-1/2" squares with slots to clear the mounting bolts. But it always bugged me to know how un-solid that shimming method was - with all the air under the sides of the column's base, and shims only under the corners.

I have NOT tried this yet, but I thought of a possible better method (emphasis on "possible"). Visualize the bottom rectangle-shaped surface of the column's bottom, where it meets the machine's base. When tramming with shims in the corners, one of the corners will remain un-shimmed, while the diagonally opposite corner will become the highest point and therefore shimmed with the thickest combinations of shim material, and the remaining two corners will be somewhere in between. So - if it could be determined the thickness value of the high corners and the two somewhat-lower corners, it might be a lot of trouble but it seems to me that a shimming arrangement could be made using strips of very thin material (maybe .002" or .003"), shingled with succeeding layers of same-thickness but shorter shim strips. Here's what I mean:



It would have to be worked out on paper first, but a shim arrangement could be made so that it would be stepped like stairs so that the high corner would have the last little bit of shim material, and from there tapering down to nothing under the low corner. They could be bonded together with super glue. I would also make a bottom layer of a full rectangle from any thickness of shim material.
...Doug

 

[Zoltan]

It wasn't clear from your posts, but the column is only supported at it's four corners, with about one square inch of mating area at each corner.

On my mill I ended up using a 0.0015" shim at one corner, 0.0015" on the opposite corner, and 0.003" on the corner in between. As mentioned above I use 0.5" wide feeler gauges for the shims. After reexamining just how much of the mating surface the two shims cover side by side, it looks like I'm getting about 80% coverage, if not more. I think that's pretty solid. There really isn't any air under the sides of the column's base when using two 0.5" wide shims side by side.

I've also though about the wedge shaped shim, but the thickest shim I'm using is 0.003" which is really quit thin, and the difference in height between the inside and outside edges of that corner are so small as to be negligible.