Re: Modifying an X-Y table - ACME - for fun and learning

> Moving on, I'm a bit confused about the reference below. Acme IS a

29

> or so degree thread, and WILL "close up" (As Jan R mentioned) by
> squeezing it (To use Sven's old idea, like squeezing the bun of a

hot

> dog). An Acme thread simply has wider crests and root spaces, when
> compared to vee thread. This increases its strength.
>
> A SQUARE thread would behave as Dave mentions...

op's I was picturing my vise and the screws in it. Thinking faster
than the words are typed.

A really bad tap in the hole creates a problem. the backlash on my
vise is about 20 thou. to close a 29 degree angle on a 20 thou gap
would be about 18 thou squeeze...

I did not measure the OD of the hole in the casting and the ACME rod,
but a really wide thread tap will not squeeze on the thread angle
before it clamps on the shaft.

>
> BTW, carefully made, these xy vise
> machines can easily repeat to .001"
>
> (That's with the 1/4-20 threaded rod,
> NOT the original screw)

Did anybody ever run force calcs on a 1/4-20 threaded rod ?

It seems that a 6 inch is not too bad, but at some point it will bend.


also, did anyone ever find the reference to ACME vs. threaded rod and
rod materials and what grade..... ?

I have to use zinc coated all-thread but not purchased threaded rod
for such a project. I'm thinking SS.

Dave