Re: [CAD_CAM_EDM_DRO] Re: Ballscrew balls ?

hi ballendo/all-


CNC Plans <http://www.fignoggle.com/plans/cncplans.htm> (DRO too)
HF 8x12 Lathe, Mini-Mill, How-To's and More <http://www.fignoggle.com>
NEW! Sieg X3 and Super X3 Mill Information <http://www.superx3.com>

On Fri, 7 Apr 2006, ballendo wrote:

> --- In CAD_CAM_EDM_DRO@yahoogroups.com, figNoggle <david@...> wrote:
> >interesting, what kind of ballnuts have different sized balls and why?
>
> Higher grade (ground) ballnuts use two sizes so that the balls rolling
> the "wrong" direction are not load bearing.
>
> Think about it, in the loaded state, a given ball is rolling against
> both its neighbor balls AND the housing. Causing sliding when all
> balls are the same size. Now sliding is a VERY bad thing where
> efficient motion is concerned...
>
> If every other ball is smaller, then the ones going the "wrong way" do
> not slide against the housing, only their neighbor balls. Sliding is
> reduced.
>
> With the cheap load-bearing-grade ballscrews and nuts we often find
> being used in DIY-CNC, the balls and housings themselves are so
> inaccurate as to make this two-size ball loading all but useless.

thanks. makes sense.

>
> But you CAN improve things greatly by using oversize balls and running
> them in, and then re-loading with fresh--oversize--balls. It's a very
> good way to maximise the effectiveness of your inexpensively purchased
> components...
>

what size do you use? i haven't gone through all the iterations of sizing,
but it seems that off-the-shelf at the major catalogs will have only
1/8"dia. (0.1250") with the next size up being 3.5mm (0.1379").

with the limiting dimension here (just ballnut) being the ID of the
bearing race (don't know what it is, but it's clearly <0.1379"), what's a good
range to use for oversizing?

thanks!

david


> Hope this helps,
>
> Ballendo
>
> P.S. The ball nut housings--and linear bearings--use a "gothic arch"
> form rather than a semi-circular one for the same reason; it
> prevents/minimises sliding and promotes rolling. Golfers understand
> this from putting!<G> (Masters week, why not<G>)
>
> And keep in mind that the round balls themselves become ovoid under
> load...
>
>
>
>
>
>
>
>
>
>
>
>
> Addresses:
> FAQ: http://www.ktmarketing.com/faq.html
> FILES: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO/files/
> Post Messages: CAD_CAM_EDM_DRO@yahoogroups.com
>
> Subscribe: CAD_CAM_EDM_DRO-subscribe@yahoogroups.com
> Unsubscribe: CAD_CAM_EDM_DRO-unsubscribe@yahoogroups.com
> List owner: CAD_CAM_EDM_DRO-owner@yahoogroups.com, wanliker@..., timg@...
> Moderator: pentam@... indigo_red@... davemucha@... [Moderators]
> URL to this group: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO
>
> OFF Topic POSTS: General Machining
> If you wish to post on unlimited OT subjects goto: aol://5863:126/rec.crafts.metalworking or go thru Google.com to reach it if you have trouble.
> http://www.metalworking.com/news_servers.html
>
> http://groups.yahoo.com/group/jobshophomeshop I consider this to be a sister site to the CCED group, as many of the same members are there, for OT subjects, that are not allowed on the CCED list.
>
> NOTICE: ALL POSTINGS TO THIS GROUP BECOME PUBLIC DOMAIN BY POSTING THEM. DON'T POST IF YOU CAN NOT ACCEPT THIS.....NO EXCEPTIONS........
> bill
> List Mom
> List Owner
>
>
> Yahoo! Groups Links
>
>
>
>
>
>
>