Re: rolled ball screws

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "mayfieldtm <mayfiet@i...>"
<mayfiet@i...> wrote:

> There is a guy on the web (Jeff Davis) that
> sells plans for building your own preloaded
> ball nut assembly.
>
> His address is http://www.homecnc.info/
> He says you can save 50% over buying new.
> Very nice site with lots of info and photos.
>
> I've purchased preloaded nuts from Rockford.
> I adjusted them by tighting them until the
> wavy springs were flat, and then backed off
> just a little. (3-5 degrees)
>
> Tom M.

This backing off is just the thing I am talking about.
If the backlash of a single nut is lets say 0.004 inch
then backing off the second nut by this amount or more
would reduce the function of this arangement to be a
mere damper when movement against the spring exeeds the
amount of preload.

This will probably result in a nice feel of motion on the
spindle because the torque of turning will be very constant
over the entire range of travel even so the effects may be
elusive.

On the other hand a Fixed position of the two nuts would
result in a feel that makes any variation in pitch on the
Screw very noticeable by requiring more torque to overcome.
But this would allow adjustment to reduce the backlash effectivly
in both directions to the amount of the largest pitch
missmatch within the length of the two nuts.

Question is what is most practical under real conditions?

Are the big MFG's of preloaded Nuts "full of it" for insulting
our intelligence for offering this kind of solution
Or
is this the most practical way of doing it?

What is your take on this?
Thanks