View Full Version : Skimming the mill bed

Robin Hewitt
23-01-2010, 08:51 PM
I skimmed a few thou of my bed today. Largest endmil wouldn't quite reach the front edge so I used a boring head set to a 30mm radius.

It just missed in the top right hand corner but I have to remove another 3 thou anyway to lose an accidental dent I chopped in it several years ago.

Q1: I did the first skim with 4 parallel passes in the X axis, is there an approved, better way?

Q2: I think you cut cast iron dry, but an experimental smear of Rocol RTD seemed to improve the finish somewhat on the first pass. It could just be the tool was blunter for passes 2, 3 & 4. What thinkest thou? :nope:

I put a DTI in a chuck so it revolved around a 4" radius arc, measuring distance to the bed at the cardinal points to make sure it was square. Got .002" difference in the X and .001" in the Y :naughty:

23-01-2010, 09:03 PM
you're a braver man than me Robin....

I think I'd have taken it to be ground..

05-02-2010, 04:17 AM
I was making something with a large ali casting and when i first got a mill I only had a boring head, so I faced the casting like you did you mill table.
The problem I had was the HSS wearing, tried coolant not a lot better. When I made a flycutter I put carbide inserts on it, I can face 10 castings with
no sign of wear.

Robin Hewitt
05-02-2010, 11:08 AM
I want to skim another 2 thou off it, but since I lost the accidental gouges I'm getting a bit wary of removing any more meat.

The best lube for cast iron seems to be humble paraffin.

It has two hard spots. I know exactly where they are and may create a tool path that avoids them until cut end.

The boring head was the wrong tool to use. Need more rigidity.

I did have success insetting a 10x10mm bar of gauge plate square along the back edge. The required accuracy was way beyond the ability of my calipers so I wound up skimming 5 microns at a pass until I got a fit. Eventually got to the point where I could tap it in.

Hopefully that means the bar was bent rather than me cutting a 'banana' :whistling:

The bar stands 8mm proud, gives me something square to line up on and will have a doo-dad on the top to hold a splash guard. I am fed up with losing coolant when the workpiece precludes dropping a sheet of plastic in a T slot. I've tried all sorts but everything leaks and is a right royal pain in the bum. Time to do the job proper I thought.