Grade 25, as we've discussed recently, is the usually the lowest (loosest) commercially-available grade of loose bearing. Fifty microns of diameter variation sucks IMO!
Grade 3 is generally the best (tightest) commercially-available grade, and is over eight times more uniform than Grade 25..... Additionally, good bearing manufacturers sort for actual diameter (generally breaking down a specific size in to three or so tight ranges). Then they build bearing units with matched balls from these sorted groups.
Cheers,
Greg Parker A2 MI USA
Pete G. wrote:
> Grade 25 is pretty darn good.
> Sphericity: .000025", allowable diameter variation: .00005".
> Maybe the Campy sets are matched, or maybe they came out of same batch
> which
> would sort of constitute being matched.
> I don't think replacing the worn balls is really the way I would go.
> Because they started out as high quality balls does not mean they're still
> round as they were when they were new.
> In the scheme of things balls are still cheap.
> I take them out and after looking for damage throw them in the scrap can.
>
> Go to McMaster-Carr's website and search for balls, click on Chrome Steel
> Balls, select a size and there on the page is a link to a pdf file showing
> a
> chart of grade and tolerances. http://www.mcmaster.com/
>
>
> Pete Geurds
> Douglassville, PA