Re: [CAD_CAM_EDM_DRO] Affordable ball screws

John wrote:

> Time to show some stupidity, but why do we want to create the hydrodynamic
> screw again? I remember it's something to do with not having to by true ball
> screws. Seems like one of those money saving plans that actually ends up
> with you having bought a brand new hydraulic pump and hundreds of pounds
> worth of fittings by the end.

Yes, I'm sure you are right! If people want good screws, they could actually
make their own ball screws and nuts. They are tricky, but not that impossible.

> This one will probably write me out the discussion right away (Keep in mind
> my newbieness to practical milling), but why can't the holes be drilled into
> the nut? The way I remember it being arranged was the screw was sitting
> between the bearings on each end of the table and passed through the nut on
> the saddle. If you have holes all along the nut aren't you going to have oil
> dripping out of 90% of it?

Yes, that was the idea. The holes would be tiny, letting a fine film of oil flow
out across the flanks of the threads throughout the length of the thread in
the nut. I suspect you'd need to make the nut in two halves to do all this
work. The thin film of oil flowing across the threads, in a condition of high
shear, is what provides the hydrostatic float. I don't know if anyone has ever
made one of these, I was just suggesting it was theoretically possible.
I think the originator of this thread figured he'd just pump oil into an ordinary
nut and have a totally stiff, zero backlash nut, but I suspect it is a lot more
complicated than that.

Jon