Re: [CAD_CAM_EDM_DRO] Long Acme threaded rod

Not really.

Acme is a std defined threadform, and you can get inserts for threading
it from all manufacturers.
So it the metric equivalent.

The problems are multiple-
Critical speed, which with far too thin 0.5" or 12.7 mm threads over
1500 mm are about 300 rpm. (aka whip).
Wear. Use ballscrews.
Repetability. Thin is not good. Thicker is better.
Accuracy. Not really an issue. Homebrew machines and jobs dont really
require accuracy - they require repetability. As long as to pieces are
built to the same relative position, whether that position is at say
absolute 1000.10 mm or 999.90 mm (or 0.20 mm error) is usually immaterial.

In cnc use, screw wear especially nut wear, is about 100x faster than
with manual machines.
Thus an acme screw will wear out almost immediately on a long screw,
like 1500 mm.

Consider running back and forth 1000 times.
This would be 1.5 kmetres, and you would already have significant backlash.
This would be the case of a large engraving job, running maybe 1 day.
The faster you run, the faster the wear.
Of course, a cnc machine can run slow, reducing the wear a lot.
Thus the same engraving job now takes 2 weeks.





If you try to get multi start acmes, you can find them, but

>
> the nuts must be made for a particular brand of acme as I understand
> the actual thread form will vary from manufacturer to manufacturer!
>

--
-hanermo



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