Re: [CAD_CAM_EDM_DRO] Help! Ball Nut Catastrophe

> Well, my curiosity got the best of me. I was cleaning a greasy,
> rusty linear lide with a nice ball screw and nut and decided the nut
> needed cleaning also (it nor the screw is rusted, i was just trying
> to remove old grease). i have never worked with ball screws and did
> not know that the ball were ready to jump out at me when i removed
> it. i scratched my head, cleaned the nut and all the balls and
> figured it couldn't be that hard to get them back in there properly.
> After about the 10 disassembly/reassembly i have resorted to this
> global request for help. the problem is that when i reassemble and
> put all of the balls in the nut and some in the tube that runs
> diagonally along the outside of the nut and fasten it in place and
> grease it, the nut spins freely a few turns then binds. some of the
> balls will even escape the nut through the felt wiper. the screw is
> parallel with the travel of the slide also. before i ever removed
> the nut from the screw the motion was flawless. is there some secret
> to this or have i cost myself serious dollars. surely getting the
> balls to run the internal race correctly isn't impossible. please
> help.

Check to make sure that you didn't somehow damage the little
'diverters' that guide the balls up out of the groove and into the
return tube - on mine, these are just a sort of spur on the end of the
return tube. Also make sure the return tubes are inserted all the
way.

All the balls have to be between the diverters.

A usefull tool is a mandrel of the diameter of the thread root, which
can be used to retain the balls. If the screw has a turned down end,
the mandrel should be a tube which will fit over that part and allow
the nut to be turned directly on a shaft.

A good workspace is an old blanket spread in the middle of the floor.
Sit on the floor. If you drop anything, it won't bounce are get far.

Some people use grease to hold the balls in place as you feed them
into the nut or to the hold few in the return tube while you put that
one, if you use the return tube holes for feeding. I do it dry, by
puling the mandrel part way through the screw so that I can drop balls
in one by one just inside of the diverter.

You should mike enough of the balls to make sure all are the same
size, rather than alternating load carriers and spacers. If there are
different sizes, you will need to sort them and devise a sensible
pattern based on their relative numbers.

Chris Stratton

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Christopher C. Stratton
Engineer, Instrument Maker, and Horn Player
ccs@... 617 628 1062
http://web.mit.edu/~stratton/www/brassbuild.html