I dont really get what your saying still sorry.
I understand the helix angle of a 3 acme on a 7" dia is 0.6513. What im having trouble understanding is what you want done with the tool.
1 mill the bottom of the tool so it drops 0.6513 deg but then the bottom of the insert on the back stide would rub.
2 tap the tool out the toolpost 0.6513 deg this would change the thread angle. |