"Spehro Pefhany" wrote in message
...
Why and where would you want to use one?

TIA.

Best regards,
Spehro Pefhany

Assuming you're making reference to a left hand spiral, they are made to
counter-act the forces where heavy cuts tend to pull the end mill out of a
collet. I suppose the concept is that it's better to have your cut shallow
out instead of the end mill pull deeper, which simply leads to the end mill
pulling out all the faster if you're doing pocket work and cutting to a
bottom instead of through the material. The other negative is if you're
cutting near the table and it pulls out unnoticed, you damage the mill
table. While they aren't routinely found, nor used, they serve a valuable
function and are worth having for that special job where you have problems.

Years ago, when I was making some master tracer templates for the Boeing
747, I scrapped a large superstructure template when a 1" end mill pulled
out in just this way. It happens.

Harold