"Tom Gardner" wrote in message
. net...

So, really it depends on the diameter of the tube so as the teeth are
entering each wall with the right timing...but then the distance between
the cuts is constantly changing...Now I'm confusing myself...

No it just means there should be three teeth (or more) across _any_
cross-section being cut. If you were cutting a webbed extrusion with six
1/4" walls, it would be still 12tpi. The 1/4" wall is the factor.

LLoyd