Plastic bearings in Ball Nut???

[java77man]

I decided to disassemble a ballscrew/nut that I purchased on ebay. It was
listed as having "some wear", when I received it, I figured it was indeed
too bad to use unless I "fixed" the backlash in the nut.

However, as I disassembled the nut, out came some ball bearings that were
translucent plastic, not steel. I collected the plastic bearings into one small bottle and the steel ones into another. When done, there was as many
plastic bearings as steel.

Has anyone ever heard of "plastic bearings" in ball nuts???

Maybe I have a shot at "fixing" this ballnut by replacing these plastic bearings
and the steel ones with "all steel", what say anyone?

Jesse
(java77man)

[Mike Nash]

I was just reading about this last week in a PDF someone had posted a link to. But it's at work and I don't remember where I got it. The plastic balls are spacers to reduce friction and that "gritty" feel a tight ballnut can have when the steel balls slide against one another. They reduce the load capacity by about half due to only having half the steel balls.

[java77man]

Mike:

Thought I was going crazy for a second. Thanks, for the info about
plastic used for spacers. Definitely, I will try to replace with all steel and
see if that helps.

Thanks again.
Jesse
(Java77man)

[ironDigit]

please do note that,

ballnuts are filled with not equally created steels balls(the ones that are all steel).
i heard of manufacturers using smaller balls as spacers in between all the slightly large balls to reduce friction when the run against eachother and this is an aspect to wreckon with if you want to end up with a smooth ballscrew.

i neer heared about plastic balls but it does stroke with spacing the actual loadbearingballs cause i can imagine what happen when they run against eachother.

so lots o measuring and read lots of nccam's post's for lots o info and lots of luck to ya!

[java77man]

Mike and ironDigit:

Upon further searching on ebay I find that the "plastic bearings" are
actually "Nylon Bearings" which at least one seller is listing as Precision
Grade 1 Natural Nylon Bearing of 1/8" diameter, quantity of 50 for $5.00

I found that my steel bearings are .1266, so I will probably buy the .1263
size that I found listed.

Thanks for all the input guys!

Jesse
(Java77man)