Re: [CAD_CAM_EDM_DRO] Delrin was (Re: all-thread question

Actually, I'm just simulating a hob. Chuck the Acme tap in the
lathe-chuck. Install a 'live' dead-center in your tailstock and locate in
the center-hole on the "start" end of the tap, for rigidity. Make a
fixture, attached to the cross-slide, to hold a gear blank (sized for the
number of teeth you want, vs the pitch of the tap) so it's axis is
perfectly vertical, and centered exactly on the CL of the tap (now a hob).
The blank must be 'driven' to achieve the number of teeth you want on the
gear. I'd use a set of 1:1 miter gears right off the shank of the tap, and
a subsequent 'geared-down' train of gears to get 20 or 25 teeth. Now, as
the tap is rotating in the chuck, simply advance the cross-slide ass'y into
the hob, until you reach the desired pitch dia. It'll take some math, but
not at all insurmountable. You'll generate a gear with the exact helical
angle you need to roll on a threaded-rod 'rack'... and, since the tooth
contour is semi-circular, it should follow linear axis of the threaded-rod
pretty well.

RayHex

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> From: Russ Revels <n4ft@...>
>
> By the way, Ray what is a hob or hobbing?
>
> Russ N4FT