Re: [CAD_CAM_EDM_DRO] lead screw or all thread

Rick Miller wrote:

> Could all-thread be used to position the work piece?
> > > Would all-thread wear out too fast?
> >
> > Yes, and even before that, it would probably not be accurate enough
> > even for woodwork. Also, unless you used a very large size, it would
> > have to spin so fast to get any work done that it would surely devlop
> > 'whip' and develop a bend in the middle.
>
> If this is what he's referring to:
> http://www.williamsform.com/Threaded_Rods/Grade_75_All-Thread_Rebar/grade_75
> _all-thread_rebar.html why would it need to be spun so fast?

A lot of people doing woodwork want feedrates in the 200 IPM region.
These threaded rods are a bit coarser threads than the common US
stuff, but that will still take a lot of RPM to get those sorts of rapid feed
rates.

> It does say
> something about a "6-10% elongation", so I'm guessing any hopes for accuracy
> are out the window anyway...

This pertains to how much it stretches under rated load. But, this stuff
is designed to have the nut put on once, turned to some tightness and left
alone
for the life of the building. I suspect this thread could be a self-binding
thread, exactly the worst for a machine leadscrew.

Jon