Thinking about it further, that third contact point would always be against
the nut groove, scuffing against it at a point in the arch that the larger
balls would otherwise never touch excepting for their preload.....
And so......me thinks the 'every other ball is sized smaller than the others
deal' is most probably just an old wive's tail.....
On Fri, 23 Jun 2006 21:29:48 -0700, "PrecisionMachinisT"
I'm wondering now too .... I think I recall they we used them
but cannot for the life of me recall assembling them but suspect
that I did ... perhaps my vague memory fails on me doing
that bit of assembly.
Perhaps different makes differ too though ...
The bearing supply house is the ticket....
Precison ground ballscrews are packed with balls that are sized
specifically for the grind fit of the ball nut. Particularly if the
screw/nut has been reground. The balls are sized in tenths. so you
normally can't just by a bag of .250 balls from mcmaster-carr etc... you
can probably go over to Ballscrews Inc (or something like that) they are
in San Jose, and get them to at least size the balls you currently have,
and maybe if you are lucky sell you a package of 100 balls. If they are
exactly .250 then you can get some from Mcmaster-carr.
Don't use WD-40. It is not a solvent, eventually it will turn into a
glue. Use MEK or acetone as a degreaser/solvent. The lubricant will be
way oil if you are going to use it in a machine that has a lube system.
You don't want to mix greases & oils, otherwise you get sludge.
Otherwise use a moly based grease.
Re-install the balls by removing one of the sheet metal recirculation
covers on the nut, and droping the balls in one at a time, as you rotate
the screw. You will want to carefully leave one ball less than tight (a
little slop in the recirculation cover) to finish. Otherwise it will
bind when you screw the cover back on.
Make sure the entire nut, covers and ball is absolutely clean, otherwise
you will destroy the screw, nut, or bearings on the first rotation.
If you can get to technical engineer at NSK they can give you better
instructions than I, and give you specifics on the type of grease they
use, exact numer of balls, material etc...
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