Partially supported inner bearing surface
Partially supported inner bearing surface
(OP)
Hi all,
I am looking into an application of an "unfortunate" square-peg-in-a-round-hole. I need to fit a 40-mm square extrusion into a 50mm ID bearing.
The application is low speed, <500RPM with low loads (robotic arm).
I am looking into turning (lathe) the square 40mm extrusion so that I end up with 4 rounded corners, with an approximate arc coverage of 7mm per corner (so 7mm supported times 4). I would re-anodize to restore the surface hardness after.
I would thus have around 20% of the nominal bearing surface covered, equally distributed.
Does anybody have any pointers or applications where they've seen this before? Should I be worried about inner race cracking?
Thanks
Jonathan
I am looking into an application of an "unfortunate" square-peg-in-a-round-hole. I need to fit a 40-mm square extrusion into a 50mm ID bearing.
The application is low speed, <500RPM with low loads (robotic arm).
I am looking into turning (lathe) the square 40mm extrusion so that I end up with 4 rounded corners, with an approximate arc coverage of 7mm per corner (so 7mm supported times 4). I would re-anodize to restore the surface hardness after.
I would thus have around 20% of the nominal bearing surface covered, equally distributed.
Does anybody have any pointers or applications where they've seen this before? Should I be worried about inner race cracking?
Thanks
Jonathan





RE: Partially supported inner bearing surface
Even before it cracks, yours will suffer from reduced stiffness in certain directions, and will make funky noises.
Better to bush the bearing ID to fully support it, and terminate the bushing to the extrusion separately somehow.
Mike Halloran
Pembroke Pines, FL, USA
RE: Partially supported inner bearing surface
Are you concerned with a few 'thou radial ( diametral) clearance?
Maybe use a 1-1/2" square bore agricultural bearing and reduce your 40 mm shaft ~ 0.074 "?
http://www.ntnamericas.com/en/website/documents/br...
Tolerances on the square shaft were not easily Googled for some reason
RE: Partially supported inner bearing surface
We once needed to make a test bench with two 12 mm thick steel supports where we put two 6205 bearings. It was necessary to change the bearings easily and we made a two mm slot in each support so we should be able to pry open the bearing seat and replace the bearings.
It never worked. There was practically no load at all but we could hear each ball bumping across that slot at low speed and we destroyed the bearings very quickly when running at 1500 RPM. Or, rather, we didn't let it run that far. The noise wasn't bearable.
Your 20% coverage is a lot less than our 98 - 99% Don't do it.
Gunnar Englund
www.gke.org
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Half full - Half empty? I don't mind. It's what in it that counts.
RE: Partially supported inner bearing surface
I'll think of something else,
Thanks!
RE: Partially supported inner bearing surface
RE: Partially supported inner bearing surface