Xaxis Trouble For A Newby

[Doublearrow]

I've got an old rusnok mill mounted on a different base I can't recall at the moment. I don't do much work on the mill but it comes in handy when knifemaking. My problem is milling left to right. If I piece that's known to be flat/parallel mounted on the table or on parallels in the vice and I try to take say .010 off the top of the piece the further I move to the left the more it takes off. I can't make a flat parallel piece. In my mind it's not a tram issue because if the head is tilted 45° it will be filed the same 45 all the way across the table and not dig in further left to right. Any ideas? I've tried you tube videos and such but don't see anything that deals with this issue. I'm just learning as I go.

 

[Micke S]

It seems as the table is not perpendicular to the column. The table may be possible to shim.

 

[planeflyer21]

It could be any number of issues or combination of issues.

How are you holding your work (knife)? Is the machine clean and free of chips inside? Are the gibs tight and properly adjusted? Does the table have low spots? Is the spindle tight? Do you have the other axes locked when moving in X?

 

[dlane]

Vice not level ?
I'ed check the vice

 

[Tony Wells]

Mount an indicator so that you can trace the table position in the -Z- axis to see if it "falls off" as you move to the extreme ends. It's not uncommon for wear to allow the weight of a table to cause it to tilt, for lack of a better word, as you get off center. If the ways are worn, and the gibs are adjusted to be correct in the center third of travel (as is common), it may also tighten up towards the end. But just because it's tight doesn't mean it's straight.

 

[RJSakowski]

I've got an old rusnok mill mounted on a different base I can't recall at the moment. I don't do much work on the mill but it comes in handy when knifemaking. My problem is milling left to right. If I piece that's known to be flat/parallel mounted on the table or on parallels in the vice and I try to take say .010 off the top of the piece the further I move to the left the more it takes off. I can't make a flat parallel piece. In my mind it's not a tram issue because if the head is tilted 45° it will be filed the same 45 all the way across the table and not dig in further left to right. Any ideas? I've tried you tube videos and such but don't see anything that deals with this issue. I'm just learning as I go.

In order to make a surface parallel to the table surface, the plane of the table has to be parallel to the x and y ways. You are right in that it is not a tram issues nor is it a matter of the column not being perpendicular the the table. In milling a horizontal surface, the table is moved beneath a stationary head. A non perpendicular column would be seen as a spindle out of tram. You would see the leading and trailing edges of the end mill cutting to slightly different depths but, although the surface will look ugly, it would be parallel to the table surface overall.

You can check your table for parallelness to the x and y ways by mounting a test indicator in the spindle and sweeping the table in the x and y directions. The indicator should not move during the sweeps.

 

[British Steel]

Do you have a dial indicator, and some way of mounting it in the mill spindle? If not, it's time to get Equipped!
After adjusting the gibs to almost-tight, with an indicator in the spindle, put one of your parallels or a piece of flat plate glass on the table, move the table through its range of movement in X and Y and note how much difference (maybe draw a little map?) - if you don't see a difference, good, the table's flat to the ways - if you do see a difference then the table's top surface and the ways are out of parallel, this may be down to wear on the ways (underside of the table, most likely). This is NOT a test for tram (spindle at precisely 90 to the table), for that you need to sweep the indicator around, held in the spindle, and compare at the extremes of X and Y (as far as the indicator can reach, anyway!)
IF you find wear in the ways or the saddle / table, it's not an easy fix - it's likely to involve scraping (possibly requiring rough machining first) and some *precision* measurement if you don't want to make it worse... The Connelly machine tool reconditioning book in the Machine Restoration part of the forum gives a good idea of what's involved - not for the faint-hearted though!

Dave H. (the other one)

 

[Doublearrow]

I appreciate the replies. I have a DTI but will have to find a way to get it chucked up in the mill.
I've held the pieces in 3 different ways why trying to figure out what was going on. In the vice clamped to a 123 block. Clamped in the vice with a parallel I made (I understand it's not accurate but it's more accurate than the mill is off, and I also clamped the piece directly to the table. I made surfaces were clean in the vice and on the table. It's a rusnok heads mounted vertically into a Burk horizontal. I will check some of the stuff mentioned on here over the next few days and see if I can come up with something.
I use the mill for cutting the lock lugs on a kickback knife more than anything. But I also have a kuhlmann pantograph mill I do inlays with. I was going to use the mill to rough out the larger areas to a certain depth and clean them up on the pantograph mill. I found this problem when I roughed one end of a liner to .030" thick and the other end was .020". The stuff I had done until this point this was not an issue.
Again I appreciate the information and time taken to help me out.