"Tom Gardner" wrote in message
. net...
Yabut the tube has two 1/4" walls being cut at the same time so...6 tpi!!!

Nah.... three teeth across any given cross-section! Otherwise, you get
grab'n'chatter.

In real life, coarser (sharp) teeth and light cutting pressure works really
nicely for 6061.

I cut through a total cross-section of a few hundred square inches of 6061 a
month making moulds for fireworks components. Dry cutting at 800fpm with a
fresh 10tpi blade works for everything down to about 1/8" walls, so long as
I watch the down-pressure on the thinner material. As long as at least two
teeth are fully supported in each cut area, chatter and surface finish
aren't too bad.

LLoyd