[sswitaj]

Hi Guys;

Got a weird one.

One of my clients is a company that does some specialized 3D photography. about a year ago, they purchased some small “camera sliders” from an outside vendor. These devices move the camera a few inches left and right with each frame to accomplish the 3D perspective shift.

Recently, they've been noticing some instability with the image, the linear glide bearings used were sometimes developing “slop” at one end of the (repetitive) travel.

Close examination revealed that the bearings seem to be carrying less than their full complement of balls, sometimes the travel was such that the balls developed gaps on opposite sides of the bearing and allowed the bearing to “rock” on the rail.

The bearings are SFK RSR-15W series, a hefty bearing (2.2”sq) on a solid rail (42mm), apparently chosen for stiffness since the load rating is gross overkill.

We hypothesize that during fabrication bearings were removed from the rails so the rails could be cut to size (they're very hard and would have been hard to cut without damaging the bearing). Then during re-assembly, many balls were lost in at least some bearings.

Sadly, this would not have been out of character for the fabricator. Over the last year a close examination of his build quality has shown, well, significant issues in this regard.

But now I have to fix these, which brings me to my question. Can somebody please point me to some documentation about how to refill linear glide bearings?

It seems fairly straightforward - get some balls, fill up the race, put in a drop of light oil, and bottle it up - but I'm not sure how many balls I should have in there or how tightly they should be packed.

This just isn't my area of expertise, and I'd appreciate it if someone could point me to some answers. The manufacturers' websites are mum on the issue.

[Mike Everman]

You can send the bearings to THK for service. The distributor for your area will know how to do this. As I recall, the rsr's have no ball retention, so take the block off the end, and it's balls everywhere.

Sounds like your vendor lost a lot of them! It's unlikely that you'd find the right size balls to fill it yourself, linear bearing makers have bins full of balls in micron increments so they can reliably preload these bearings. You might luck out, with a stock size you can find, but I doubt it.
Take one out and mic it, see what you're looking at. Oddly, Japanese bearings are often English size balls.