Re: [CAD_CAM_EDM_DRO] Re: ball screw preferences

So you're saying the ballnut is flexible to conform to different internal circular diameters?

Or the balls are used as a fulcrum to deform the cast iron nut to conform to whatever pitch diameter they feel like making that day?

Or does a round ballscrew and disfigured ballnut not matter?

Or D none of the above? :)

Seriously, there is a reason not everyone has adapted this method. If it was that easy...

Shaft collars are reamed to a nominal size and usually used where a collar only is supplied that way the customer can get a tight fit in the field if the shaft is a thou under or over. The true intent of a .500" ID split collar is meant to be mounted on a .500" OD shaft. It's not a one size fits all. The connection is rigid, is meant to be a way of securing to the shaft with out setscrews, drift pins, etc. Tight fit without pressing.

You mentioned the other day, that all single nut setups have at least .003" backlash. This is not true. Hiwin screws (inexpensive) are single nut and zero backlash. I've installed them and I've checked them, backlash in the screw was zero. Just did a retro for a guy in Fla on his 10X50 clone, Hiwin single nuts, no measurable backlash. He did have .002 on both X and Y, then we replaced the single row bearings with double row angulars and all backlash gone (6204 to a 3204). Alot of the old Bridgeport sets were single nut and had no backlash when new. The Rolled Rockwells in one of my mills are zero backlash as well, but they are dual nut setups. Can one lock the table and push the handwheel a few thou? Sure can, thats not backlash. Thats applying tons of force on the Yoke, endplates and ballnut and resulting deflection.

Ron

ballendo <ballendo@...> wrote:
Hello,

This is true if the circle is unconstrained. But in the case of
these ballnuts the circle(ballnut body) will be supported by the
balls, and they are running in a helix, fully surrounding the
circumference of the ballscrew.

So the net effect will be the same as if you had placed a hose clamp
or clamp-style shaft collar around a cylinder with a helix of balls
between. The hoseclamp or clamp-style shaft collar will deform, but
if it is engineered with this deformation in mind, the balls will
cause it to deform fairly uniformly around the ballscrew.

I used hose clamp and shaft collar as examples because one is too
thin and the other too thick to ben an effective ballnut body in
this technique. But each IS tightened around its cylinder from a
single point. And each does indeed conform to the shape of the
cylinder within. (They do not remain oval!)

In this same way I would expect the ballnut body will also evenly
distribute around the ballscrew. It appears that it does based on
Steve's good success using them. He is not an inexperienced
machinist; and would likely have mentioned if there were tight and
loose spots in the balls travel...

Hope this helps,

Ballendo

P.S. The mfr. may even pre-shape the ballnut body as an OVAL(or
other shape needed) so it deforms INTO a circle upon loading. But I
doubt that is necessary.

--- In CAD_CAM_EDM_DRO@yahoogroups.com, R Rogers <rogersmach@...>
wrote:

>
> Slitting a circular sleeve lengthwise and compressing it, produces

an oval, not a smaller circle. This would produce tight and loose
spots in the ball travel.

>
> Ron
>
>
> ballendo <ballendo@...> wrote:
> Steve,
>
> Thank you for the details. I've seen that technique (If I'm
> understanding you correctly) of BL control used by Techno Isel in

the

> A/b nuts used in their routers and sold as parts. Always thought

it

> was an interesting approach. Wondered why it didn't see wider use.
>
> With your endorsement here that will likely change,
>
> Ballendo
>
> >>B wrote:
> >>P.S. Have you used these ballnuts?
>
> >In CCED, Steve Blackmore <steve@> wrote:
> >Yes - I use them all the time, they are very good, and not that
> >expensive. The nut has a split section where the ball track is

and the

> >adjusting screw actually squeezes it reducing the clearance. The

screw

> >they sell is rolled but it seems good quality with good hardening

on

> >the outer surface.
>
>
>
>
>
>
> [Non-text portions of this message have been removed]
>

[Non-text portions of this message have been removed]