Re: [CAD_CAM_EDM_DRO] Re: How to Make a Simple CNC Machine

At 04:19 PM 10/19/00 -0500, Jon Elson wrote:

>kleinbauer@... wrote:
>
> > Who needs a $150
> > leadscrew when a $2 piece of 1/4-20 threaded rod will work.
>

I use 3/8-16 threaded rod on a table router fence adjustment. Since you
spec the accuracy in fractions rather than decimal or mm, the 3/8 rod gives
1/16" per turn (thus 1/32 per half turn, 1/64" per 14 turn etc.)

>What is the overall accuracy of the 1/4-20 rod?
>
> > I use a
> > one inch piece of rubber tubing to couple the motor to the threaded
> > rod.
>
>How rigid in torsion is that rubber tubing? Or, do you really use some
>stiff
>plastic tubing? That might be pretty good, but if you really use
>RUBBER, it
>might allow quite a few steps worth of twist to develop between the
>motor
>and leadscrew.

The rubber tubing sounds good to me. Any "skipped steps" would be in the
"winding up of the rubber tube that would catch up at the end of the cut
while at the same time create a sort of ramping/torque taming. I think I
will try it when I build my CNC router (soon, I hope).

Hugh

P.S. For the most part, selling a "beginners" guide to building CNC
Machine to this group would be akin to carrying coal to Newcastle. Good
luck on your venture.

>Jon
>
>
>
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