Bryan
23rd September 2010, 09:11 PM
Hands up who grinds rake on threading tools? My text book says not to because the angle will be wrong. Having turned a few rough threads, I wanted to find out just what effect rake would have, and if it could be compensated for. Not being maths-savvy enough to calculate it, I drew it instead. I made a 3D model of a 60 deg 1/2 x 13 tpi UNC thread, drew a plane inclined at 16 degrees, and measured the angle of the point. It comes to 59.9 deg. To heck with a tenth of a degree I say!
You may notice my thread model is made of segments rather than true curves, and this might change the result. But it's the best I could do. If someone else can model it better, or calculate it, go your hardest. For the record I did try to also model a fine thread to see if it made any difference, but I'm having some trouble with Google Sketchup. It can be a bit, er... sketchy. Anyway I intend to try grinding up a 60 deg tool, inclined at whatever, and see what happens. Maybe try a direct comparison.
You may notice my thread model is made of segments rather than true curves, and this might change the result. But it's the best I could do. If someone else can model it better, or calculate it, go your hardest. For the record I did try to also model a fine thread to see if it made any difference, but I'm having some trouble with Google Sketchup. It can be a bit, er... sketchy. Anyway I intend to try grinding up a 60 deg tool, inclined at whatever, and see what happens. Maybe try a direct comparison.