Thread: The old "trimming the mill" question

Originally Posted by RayG

Yes, we are talking about different things..

I agree, by definition you can't tram it wihout changing the X axis or the spindle axis, but you can get it to cut parallel. ( well maybe, with this mill, I'd not be too sure... )

Ray

Yeah you can but I agree with Ewan, only if you lock the X axis and feed with the Y axis. The top & bottom of the vise may be at right angles to the spindle if you shim it, but the X travel still isn't so moving the vise relative to the spindle is going to cause a movement the same as if you tilted the spindle relative to the X axis.

PDW

Originally Posted by PDW

Yeah you can but I agree with Ewan, only if you lock the X axis and feed with the Y axis. The top & bottom of the vise may be at right angles to the spindle if you shim it, but the X travel still isn't so moving the vise relative to the spindle is going to cause a movement the same as if you tilted the spindle relative to the X axis.

PDW

Yes, agreed, and if the cut was an X axis move, the Y axis would be concave by some amount depending on the tramming error and the cutter diameter. Whether it would be parallel in the Y axis would depend on if it was trammed in Y, in this case I'd be guessing not.

What you and Ewan are saying is that a Y axis move with X locked doesn't care if X is trammed with respect to the spindle axis. I agree.

The only real way to fix the problem is to fix the column to base error...

Ray

Originally Posted by RayG

Yes, agreed, and if the cut was an X axis move, the Y axis would be concave by some amount depending on the tramming error and the cutter diameter. Whether it would be parallel in the Y axis would depend on if it was trammed in Y, in this case I'd be guessing not.

What you and Ewan are saying is that a Y axis move with X locked doesn't care if X is trammed with respect to the spindle axis. I agree.

The only real way to fix the problem is to fix the column to base error...

Ray

Yes and as Andrew (I think) pointed out, you have to do it relative to the quill not the column, or you need to verify that the quill travel is co-planar in both X & Y with the round vertical column/base. I think the first thing I'd do would be to check if the quill was in fact parallel to the column and if not, work on mapping out the differences then make sure the quill is at right angles to the table. Worst case then is a slight shift in quill position in one or both X & Y axes on change of height on the head using its Z travel.

PDW

Originally Posted by Stustoys

No it wont........Doesnt matter what you do with the vice....the surface of the workpiece will exactly the same in relation to the X axis....only the bottom of the work piece will have moved a little.

I'm thinking you're talking about getting it to cut parrallel. I'm talking about tram.

Stuart

I thought about this overnight, and you are correct, there's nothing you can do with the vise that will alter the cutter path with respect to X axis moves.

Ray

Here's my thoughts on how you can operate a mill that can't be trammed.

As per the previous thoughts, you tram the vise by shimming in both X and Y directions. By rotating the indicator in the spindle as normal.. and indicating off the vise jaws.


Let's say we want a flat surface on a part, and are using a facemill.

Set up the job on parallels as normal and line up X for the first cut in the Y axis, Then you setup a DTI on the column and dial in the cut depth with Z, and zero a column mounted DTI on the vise jaws.

Take the cut in Y, and then step over in X, but when you step in X the Z will drift up or down depending on how far out of tram it is. so move Z to bring the DTI back to zero.

Now the vise is exactly where it would be in relation to the spindle if the mill was trammed..

Keep stepping across and correcting for tramming error each time by adjusting Z to bring the DTI back to zero each time.


Ray