Tramming a mini mill. Shims vs epoxy?

Alternate idea. Determine how much you need in a shim. Then make a spacer with that much angle. A small spacer won't be difficult and you can keep file and milling to get what you want. A thicker spacer will give you more "Z".
 
Lots of threads and you tube videos on how to tram a round column mill/drill. My favorite method is to duplicate the bolt spacing on the table with the quill centered on the bolt spacing. Take a DI reading at each bolt position. Zero the DI at the longest distance. Then take a reading at the 3 other bolt positions. Those readings will give you how much you need to shim at each bolt to bring the column into tram.
 
I found the 3990 to be a capable machine within its limits. Actually does some things better than my full size Wells Index (shush , blasphemous)
However I found I really needed more Z so you may want to get a column riser block an only shim once !
I had the pleasure of doing it twice. Good luck with the 3990 I think you will enjoy it, just don't push it too hard and you can turn out very nice pieces. Slower than a full-size but very nice and we are not doing this for speed are we? Enjoy the process. I have my car/truck/bike hobby for speed...and the 3990 can turn out some great carb/manifold plates !
 
jpackard56 said:
I found the 3990 to be a capable machine within its limits. Actually does some things better than my full size Wells Index (shush , blasphemous)
However I found I really needed more Z so you may want to get a column riser block an only shim once !
I had the pleasure of doing it twice. Good luck with the 3990 I think you will enjoy it, just don't push it too hard and you can turn out very nice pieces. Slower than a full-size but very nice and we are not doing this for speed are we? Enjoy the process. I have my car/truck/bike hobby for speed...and the 3990 can turn out some great carb/manifold plates !
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That's great to hear! So far I absolutely love it. It's not the biggest machine but I don't have much space in my garage anyway. I love the brushless motor and I'm sure it'll be awesome once I tram everything up and keep everything well tuned.
 
Mach Zero I just noticed that you are a brand new member. Welcome aboard. There are a lot of really knowledgeable people on here who will help you out. We are a friendly bunch. Don't be afraid to ask any question no matter how trivial you may think it is. People will answer your questions.
 
I read a post from someone who made a riser block for their mini mill and machined-in the compensating tilt, eliminating the need for shims. He claimed to have done it by utilizing the as-given column tilt, but I don't believe that would work unless a fly cutter was used (to avoid stepping the cutter over); and even then, only for one axis -- the one that is not moved during the fly cutting pass.

You probably could do it If you determine the amount of shim needed for both axes and machined the riser block to compensate.

I own a mini mill with a tiltable column so the X axis can be easily trammed. Positives and negatives there because it also can be knocked out of tram. To make my mill a bit more rigid I made a 1/2" steel plate to replace the big Belleville washer that attaches the column to the mounting block, and as part of that I added a jackscrew setup to the bottom of the plate that enabled me to tram the Y axis. Within a small range, anyway -- it applies force between the column and base to do it. If my Y axis tram had been out quite a ways I would have shimmed it first to avoid the risk of breaking the column bracket (or worse yet, the base itself).

BTW, even if you've got a very crappy drill chuck it doesn't matter when it comes to tramming your mill (unless the chuck is just plain loose somewhere). Since your dial indicator (DI) rotates along with the chuck, its plane of reference remains constant. This is the beauty of the single-DI method of tramming.
 
homebrewed said:
I read a post from someone who made a riser block for their mini mill and machined-in the compensating tilt, eliminating the need for shims. He claimed to have done it by utilizing the as-given column tilt, but I don't believe that would work unless a fly cutter was used (to avoid stepping the cutter over); and even then, only for one axis -- the one that is not moved during the fly cutting pass.

You probably could do it If you determine the amount of shim needed for both axes and machined the riser block to compensate.

I own a mini mill with a tiltable column so the X axis can be easily trammed. Positives and negatives there because it also can be knocked out of tram. To make my mill a bit more rigid I made a 1/2" steel plate to replace the big Belleville washer that attaches the column to the mounting block, and as part of that I added a jackscrew setup to the bottom of the plate that enabled me to tram the Y axis. Within a small range, anyway -- it applies force between the column and base to do it. If my Y axis tram had been out quite a ways I would have shimmed it first to avoid the risk of breaking the column bracket (or worse yet, the base itself).

BTW, even if you've got a very crappy drill chuck it doesn't matter when it comes to tramming your mill (unless the chuck is just plain loose somewhere). Since your dial indicator (DI) rotates along with the chuck, its plane of reference remains constant. This is the beauty of the single-DI method of tramming.
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Depending on how the mill is set up, you should be able to machine the riser block with bosses at the bolt locations. This will eliminate the issues with step over artifacts. I would determine what was required for shims and shim the underside of the riser to raise the riser appropriately.

While runout of the chuck doesn't matter, any radial play in the spindle could affect the tram measurement. When I check my RF clone, I pull the belt and rotate the spindle from the pulley to minimize adding any bias.
 
homebrewed said:
I read a post from someone who made a riser block for their mini mill and machined-in the compensating tilt, eliminating the need for shims. He claimed to have done it by utilizing the as-given column tilt, but I don't believe that would work unless a fly cutter was used (to avoid stepping the cutter over); and even then, only for one axis -- the one that is not moved during the fly cutting pass.

You probably could do it If you determine the amount of shim needed for both axes and machined the riser block to compensate.
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This is a really interesting idea. I'm not sure how well I would be able to execute this idea, but I would think this would be more solid than shims (probably not by too much though).

I'll have to look into this more.


RJSakowski said:
Depending on how the mill is set up, you should be able to machine the riser block with bosses at the bolt locations. This will eliminate the issues with step over artifacts. I would determine what was required for shims and shim the underside of the riser to raise the riser appropriately.
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Seems like I would have to be pretty precise with machining the riser block. I guess I would also machine the riser block after the column is shimmed/trammed to make sure it's square?
 
If you have a fly cutter I think you can determine the angle(s) necessary to tram your column via a riser block. Face the bottom of a test piece so you know it's flat, then mount it in your milling vise high enough so you can mill the top. Install your fly cutter, then center it on the Y axis of your test piece. Lock the Y axis. Then move the fly cutter along the X axis and mill off the top of the test piece -- just enough that the entire top surface has been planed off by the fly cutter. The angle on the Y axis is the out-of-tram angle of your column. You can determine the angle by measuring the thickness of your test piece at the top and bottom. The difference is the height of your triangle. The base of your triangle is the width of your test piece on the Y axis. Height/base = sin(theta), where theta is the angle. Alternatively, you can shim the lower side of your test piece until the top is flat, then use the shim stack to machine your riser on that axis.

For the out-of-tram angle on the X axis you can either re-machine your test piece or machine a second one (but exchange the references to "X" and "Y" above).

I don't think you can use this approach to create the compound angle you need on your riser block. But if you make two separate test pieces for the X and Y axes, you can stack one on top of the other and either use the combination to create your compound angle for milling your riser block: or stack them as a 2-piece riser and call it good. It also might be possible to use your first test piece to tilt your riser block on one axis, then mill its top on the other.
 
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