On Sat, 20 Nov 2004 01:25:20 -0600, Jon Elson
wrote:

Rashid Karimov wrote:
A while back I posted some questions on the subject.
In general the responses to my and prior questions were
not too good - neither was my early experience.

The 6xxx aluminum is nearly impossible to slot, as it is soft &
gummy etc. However I continued the search for the right
alloy, as I have seen it done in Russia.

I machine 6061 all the time, with no problem. I have even had
to anneal 6061 for bending, and then machine after the bend.
If you think you can plow a slot the width of the end mill
and leave it like that, it won't work. You have to mill the slot
right down the middle with a smaller end mill, then make
cleanup passes down both sides. The end mill wanders due to
the cutting forces, leaving a wavy wall. If the material is thick,
you need to mill it quickly in several passes of successively
greater depth until you break through, then do the cleanup
passes.

Jon
What works even better than running the endmill right down the center
is to bias it a little towards the climb cut side. The conventional
cut side of the slot is the side most likely to have the cutter dig in
and ruin the finish. This is because the cutter is being pushed away
from the climb cut side.
ERS