Face mill finish

[Edward]

Let me explain:

If I swipe the X axis from extreme to extreme, I have 0 deflection now, the indicator (a bit preloaded) stays on zero throughout. This is because I shimmed the column to be square to the table. That works perfectly and I've never had it so good. I used a very thin aluminium shim, the kind of sheet that you used to get from lithographic plates.

Now for the spindle: I attach the indicator to the spindle by means of one of these annoying articulated bars. So the indicator is touching the table 15cm away from the spindle. Then I swivel the spindle 180 degrees and measure the opposite side of the table. There is a difference of 0.4mm. There should be no difference in an ideal world, the reading should be exactly the same at both ends. I suspect this is due partly to a bit of spindle runout and partly to the spindle not being exactly square to the table.

Because this covers a total distance of 30cm. I don't think it's too bad.

I also did a test with a 10mm bar in the spindle, and measured the Z axis moving it up and down with an indicator just touching along the bar. Depending on how the spindle was turned, I got different readings, from perfect to some deflection, again to be expected due to spindle runout. All this measuring is enough to drive you crazy. The important thing is that the pieces are square using an engineers square and the face mill doesn't leave any ridges, just a few tooling marks which I would rather not have, but they polish off nicely anyway.

I guess I have to live with some imperfections. Next mill will certainly have a possibility to adjust both the column and the head. In hindsight maybe I should've bought a different mill, however, a different mill will have other problems. Nothing is perfect, not for that amount of money anyway.


Edward