Minimill tramming need opinions

[razzle69]

I have reached the point in my skill level where I am beginning to notice the out of tramness of my minimill. About 2 thou of nod and about 4 thou left to right.  Solid column Seig X2D. Having convinced myself that I need to fix it I am now ready to try. Shimming sounds frustrating so I found another machinist who posted that he trimmed by replacing the four mount bolts with studs and flange nuts. This allows screw adjustment of tram instead of shims. He said he had no issues with rigidity. But my sense tells me that this mounts the column on 4 independent posts instead of the flat base. So it should reduce rigidity somewhat. My question is does it matter on this size mill? The ease of tramming might outweigh any loss of rigidity. I take small cuts anyway. I can always reverse but taking off the column is a pain as the head weighs close to 40 lbs. It's a project either way I do it.

[Adasha_Machining]

Maybe I'll let someone with a bit more knowledge of smaller mills come up with ideas, because I'd have you tramming the column with shims and epoxying it with Moglice. A project, but I'd wager your mill would cut twice as deep after.

[TerryWerm]

You may need to engage in "differential shimming", especially in the nod where you only need to take out .002".   If you shim .0005" at the bottom of the column, you are going to change things by four times that amount several inches away from the centerline of the headstock. You may have to shim .001" on one side and .0015" on the other side of the column. It will take some experimentation to say the least, but be prepared to see big differences in tram with just tiny changes at the base of the column.

One other thing to keep in mind is that shimming with brass will probably deliver different results than shimming with stainless steel. Brass, being soft, can squeeze a lot more than stainless steel, being rather hard.

The base of those columns is also cast iron in most cases. That said, you will need to shim at the bolt holes and not halfway in between. You could potentially crack the base when tightening the bolts if you shim in between. Not likely if you are only shimming very small amounts, but a very real possibility if you start looking at greater shim thicknesses. 

I am no expert on round column machines like that as I have never had one. But I believe that shimming will work if properly done in the right places and the right amounts. Maybe someone else will chime in. Either way, best of luck to you, I do know that others have had good luck with shims though it was something of a hit and miss process.

[razzle69]

So it sounds like shimming is the better way to go. The differential shimming was the reason why I got interested by the stud/bolt option as it allows for that type of adjustment. But I see how the shims would be better. And the moglice would enhance rigidity. I think Stefan Gotteswinter has a video on that. I will have to order the shimstock. I don't have anything that thin on hand. Gonna take a lot of trial and error to do.

[Adasha_Machining]

So it sounds like shimming is the better way to go. The differential shimming was the reason why I got interested by the stud/bolt option as it allows for that type of adjustment. But I see how the shims would be better. And the moglice would enhance rigidity. I think Stefan Gotteswinter has a video on that. I will have to order the shimstock. I don't have anything that thin on hand. Gonna take a lot of trial and error to do.

Stephan was exactly who I was going to refer to. I have done the same procedure with a bench top lathe and a milling machine lead screw.

[chips and more]

My 3 cents is try the adjustable mounting bolt trick. Bolts with big flange nuts sounds good enough for me when that size mill is the topic. You could even add a downward pushing setscrew(s) to stiffen things up. Good Luck.

[razzle69]

My 3 cents is try the adjustable mounting bolt trick. Bolts with big flange nuts sounds good enough for me when that size mill is the topic. You could even add a downward pushing setscrew(s) to stiffen things up. Good Luck.

Hmmm, that is an interesting suggestion. I may give that a try. If I have rigidity issues I could always go back to using the regular bolts and shims.  At the very least it would be a learning opportunity.

[Piggiron]

If you really want to jaz it up trying Chips suggestion, incorporate some differential threads into it. This would add fine adjustment for tramming.
https://www.youtube.com/watch?v=ywmRv3I_dAw

[razzle69]

If you really want to jaz it up trying Chips suggestion, incorporate some differential threads into it. This would add fine adjustment for tramming.
https://www.youtube.com/watch?v=ywmRv3I_dAw

That is an interesting suggestion. I ordered some 8mm threaded rod to replace the bolts on the column. I was wondering how fine of an adjustment I would have with that. A differential thread may be a better option if I can't get fine enough resolution with the rod. Of course I would need to be able to cut 2 different metric threads. Not sure I have the tooling for that.

[chips and more]

Not sure what pitch it is? Maybe 1.25mm? So about 0.050"/360°turn of the nut. Hope my conversion and math are correct? LOL! That should give you good adjustment capabilities with finesse.

[Piggiron]

That is an interesting suggestion. I ordered some 8mm threaded rod to replace the bolts on the column. I was wondering how fine of an adjustment I would have with that. A differential thread may be a better option if I can't get fine enough resolution with the rod. Of course I would need to be able to cut 2 different metric threads. Not sure I have the tooling for that.

If you don't have the tooling, you could ask if a member here would help you out. There are at least a couple members in Texas, not sure how close they are to you. Besides, 2 heads may be better than 1 for designing it.
 

[propforward]

I had great success tramming the column on my bench mill using shims for the nod. For the sideways tram I just used the angle adjustment of the head. I never take any notice of the degree scale anyway. I never got around to doing the epoxy part but always meant to. I shimmed it exactly as Terry described - and honestly it does not take very long. The stud and nut idea sounds good but it is definitely less rigid. Now whether that matters much because of other rigidity issues with small mills is another question.