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