Kurt doesn't use an acme thread ???

[T Bredehoft]

creating more cross section area at the pitch line

4gsr almost has it. The finer thread, the larger the pitch diameter, thus a larger area to resist shear.

 

[Redmech]

I'm a heavy equipment mechanic, we use a lot of 1 1/4 fine threaded rod for puller bolts. That puller rod Caterpillar says is rated at 60 ton, I'm 99% sure that's right. I'll look at my books in the morning. Very strong.

 

[kd4gij]

I am pretty sure Kurt knows what screw is the best for the job.

 

[4GSR]

This is a little off topic. Here's a sheared out thread on some composite material we did a test on a few years back. Don't remember the load applied, it was in the 60K lbs./force range. Ken

 

[whitmore]

Wouldn't a buttress thread or square be stronger? Just asking.

There's more frictional torque in a Kurt vise when it's tightened,
than if it had an Acme or square or buttress thread.
Probably you want that friction.

My wood vise uses a buttress thread; the main benefit is that
the 'nut' is not expanded under load.
In the wood vise (it's a quick-release type) the buttress thread makes
the half-nuts not disengage under load, because the surface pressure is
axial force, not the right direction to push the nut open.

 

[whitmore]

This is a little off topic. Here's a sheared out thread on some composite material we did a test on a few years back. Don't remember the load applied, it was in the 60K lbs./force range. Ken

That's typical of failures in dissimilar materials; the stretchiest one takes
no force on the back threads, so the front threads start to shear. Then
the 'front' just moves along the total engaged distance.

I've also seen this on a bicycle rear (drive) hub, where there was more than
one 'standard' for the thread. 24 tpi(US, GB, Italy, etc.) and 1mm(French)
are very close, and the penalty for guessing instead of measuring is ... as I recall, a lot
of time spent rebuilding wheels (and a few bucks on the alloy hub part,
which failed, of course).

 

[4GSR]

Here's my favorite one I pulled on a test. The screw material is 110K psi minimum yield material and the nut material was about 35K psi class 40 gray iron. I have 56K for the shear load it took to shear out the cast iron. This was right at the minimum needed for the product. I had to go in and increase the amount of thread engagement by four threads. BTW, this was a 1.000-8 NC-2 thread. Ken