Re: [CAD_CAM_EDM_DRO] re:worm drive -> rack and pinion

On Saturday 11 November 2000 16:15, Ballendo wrote:

> 2)The fact that worm gears are not designed to be rack/pinion. This
> means the thread form (vee) will not carry anywhere near the load of
> the acme rack, and the alignment between "worm" (pinion) and "gear"
> (ready rod) will need to be MUCH more precise than std. 20 degree
> pressure angle rack/pinion. And Loads will tend to "push apart" the
> two pretty easily since the angle involved is 30 degrees.
>

good points, if the screw is suspended you would need an idler worm
on the oposite side to keep the rod from springing out of mesh
sort of like a lathe half nut setup

also the lead angle may add some side presure/torsion on the
worm and screw

> 3) The poor quality of most ready rod threads. Pitch variations/ bad
> plating/ etc. (there's a REASON these things are cheap! )
>

yep ,steer clear of the hardware store stuff ,if you do this
try to find some grade-8 ,unplated ,rolled allthread ,much better quality
or for Acme threaded rod ,you could sacrifice a short chunk to
make your own worm hob ,cheaper than an Acme tap

Brian