Also called a slew bearing or lazy susan. This is an ABS ring bearing made using 99 1/8" ball bearings. The track diameter is calculated for a circumference that would fit 100 balls, then I leave one out to add some space, which just happens to exactly be exactly 100mm diameter for the bearing track. I used .125 mm clearance on the bearing track, which is pretty tight. It still rotates without sticking even though there is no play whatsoever, but you can't free-wheel it. If you needed a stiffer bearing for something like a monitor stand then the .125 clearance would be good for that. I'll have to make another one using .2mm clearance because I need a slightly easier to rotate bearing. It's a simple thing to model and print, the only part that sucks is inserting 100 little balls one at a time. You have to press them into the track one by one, so you can't just pour them in. At least not with .125 mm clearance. The gap between the inner and outer rings is 1mm.
I found a pretty neat trick for inserting the nuts into the plastic so that they won't fall out. The nut hole is slightly undersized, then you put each nut on the tip of a hot soldering iron and press them into the nut hole. The melted plastic locks them in so you can't accidentally push them out with the screw, and you don't have to care about the tolerance of the nut hole as much as if you were trying to press fit the nuts.
The second picture is where the balls get loaded in. The inner ring is split in half to allow loading the balls, then the other half is placed on top and the two halves are bolted together.
- ring_bearing1.jpg (347.42 KiB) Viewed 3798 times
- ring_bearing2.jpg (349.45 KiB) Viewed 3798 times
- ring_bearing3.jpg (365.5 KiB) Viewed 3798 times
Experience is what you get when you didn't get what you wanted.
