Re: Why not use threaded rod leadscrews?

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Paul" <paul3507@b...> wrote:

>
> Stainless threaded rod is cheaply available in 1m (39in) lengths.
> I know the V thread profile is not square, not ideal for loads, not
> ideal friction wise, greater wear/backlash problems, not so
> linear.......blah, blah
>
> BUT I can save a *huge* amount of money on a 1mx1m wood router (3ft
> 6in x 3ft 6in). I've been quoted over £100 ($180) for a new 1 meter
> leadscrew which I think is OTT.
>
> Also is there a cost-effective source for rack and pinions? All the
> large 8ftx4ft pro routers use rack and pinions.
>
> -Paul

All-thread has a 60 degree angle and when it is under pressure, it
tends to lock up. That is the design and why nuts self lock when
bolting things together. The metal is somewhat elastic and bends
slightly imparting pressure and combined with friction, that holds
stuff stationary.

In moving things, high torque and stationary are opposite of what we
want.

BUT, for low torque applications, the stuff works well. I used a
lenght for a proof of concept unit with a 10 foot table. I left
room for a 1-1/2 inch ballscrew (for the future) but the all-thread
worked so well, it is still there.

In my recent searching, open ended belting costs around $6-10 per
foot but a 4 foot pitch belt was less than $20.00 so it could be cut
for a 8 foot table.

I called SDP about the pricing and the tech was surprized. I hope
they don't change the close belt price to make them competitive.

But, 4 pulleys at $25 each and a pair of 4 foot belts at $20 each
would put a drive on both side of a table for around $150.00

I assume the idler pulleys would be timing pulleys with grouves. not
just flat ones???? Not sure what the effects of tightinting them
and riding on the teeth would be.

Dave