Re: [ATM] OT how to cut threads

["Don Clement" <clement.focuser@verizon.net>]

> I'll also mention that Don's suggestion for reverse threading can be a bit
> dangerous if the chuck is merely screwed onto the spindle and not locked
> there.

Bob is right! One should use caution when reverse threading or reverse
rotation cutting with a threaded spindle. I  normally use a D1-4 camlock
chuck or parts are held in a 5C collet chuck so that during reverse
threading or reverse rotation cutting the chuck cannot spin off. With that
caveat, it is easy to reverse helix thread from a shoulder at .5K -1K rpm. I
get better surface finish when threading on some materials (SS, aluminum)
using the higher rpm with topping carbide threading inserts. It is not so
easy to thread (in a manual lathe) up to a shoulder at high rpm with the
normal threading method. Also I use the compound set at between 27* and
28.5* with the final cut straight in with the cross slide.
My procedure for threading is to use the compound feed at between 27* and
28.5* (for UN 60* threads). I zero the cross slide at start and feed with
compound. After cut and opening split nut, I back off cross slide to greater
than depth of thread and return to beginning of cut. Re-zero cross slide,
advance compound and close split nut and repeat cut.

Don Clement
Running Springs, California

_______________________________________________
ATM mailing list http://www.atmlist.net/