Atlas threading problem solved

[markba633csi]

Just cut some 3/8"-16 threads (my first) on my MK2 Atlas and found that the tool was drifting slightly
to the right and back again with each revolution of the spindle. I discovered the 64 tooth
leadscrew gear had a slightly crushed tooth which was causing a tight spot once per rev of the screw. Apparently there was enough flex in the banjo to transfer some error to the carriage. The tip-off was the fact that the leadscrew TPI was the same as the thread I was cutting (16). I dressed the damaged tooth with a file and all is well.
Check your zamak gears carefully folks!
Mark S.

 

[kopcicle]

Just cut some 3/8"-16 threads (my first) on my MK2 Atlas and found that the tool was drifting slightly
to the right and back again with each revolution of the spindle. I discovered the 64 tooth
leadscrew gear had a slightly crushed tooth which was causing a tight spot once per rev of the screw. Apparently there was enough flex in the banjo to transfer some error to the carriage. The tip-off was the fact that the leadscrew TPI was the same as the thread I was cutting (16). I dressed the damaged tooth with a file and all is well.
Check your zamak gears carefully folks!
Mark S.

I know this is necro posting Mark but I had none but the usual issues turning 1/2"-16 ACME.
Usual meaning turning the compound to 14 1/2 degrees and spending a bit-o-time on grinding the cutter profile, a few times...

I turned the 1/2" - 16 to make a tap for making my own half nuts. I wanted to get close with internal single point and finish with the tap. . I just used water hardening drill rod and the usual magic tricks