Helical thread cutting........ was Re: making ball nuts

Clint,

The amount of material needing to be removed might make tapping not
the best way for ball nut making. You'd probably need one of those
very long taps similiar to what are used for single pass tapping of
Acme threads or maybe multiple taps. Long taps or multiple tapping
operations don't lend themselves to production manufacturing very
well. This is a cinch for a thread milling type operation done with
helical interpolation on a 3 axis CNC mill.

No matter how the nut blank was roughed out, after heat treatment the
ball grooves would have to be ground using a machine capable of
following a helical path.

Incidently, very acceptable threads can be milled on 3 axis CNC
machines not supporting helical interpolation. By programming the
helical path in a series of very short line segments it's hard to
tell the difference between that and a true helical interpolated
part. My first CNC mill didn't have HI and my CAM system only did
two axis, so I generated the Gcode on a spread sheet.

The thread milling process opens up possibilties. Neither of my
lathes will easily handle thread cutting much coarser than 8 tpi, but
by thread milling any pitch is possible. I've done 4 tpi in steel,
no problem. The only limitation is thread length because of cutter
extension.

Doug

--- In CAD_CAM_EDM_DRO@egroups.com, Clint Bach <clintbach@y...> wrote:
> Hmmmmm.... Ahhhhhh..... Errrrr.....
>
> To make the threads inside a ball nut wouldn't it be much easier to
just
> make a special tap?????? I know it isn't all that exciting and
would be
> way too fast for a truly dedicated machinist but why not use a
tap???
>
> Thanks,
>
> Clint
>
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