raceway profile 1

[petedie]

Hello,

I've a cylindrical bearing raceway for nine loose 0.2500" bearing balls that matches 7/32" radius gauge. My question is that whether that is correct and why? Is there a specification for designing such raceways?


Thank you
Pete

 

[MikeHalloran]

The external dimensions for bearings are pretty well standardized.

The internal dimensions are not, and may be regarded as proprietary by each of the multitude of manufacturers.

A radius gage may not tell you all there is to know,
- because it's a relatively imprecise tool,
- and the geometry of the race section may not be exactly circular.

Example: Kaydon 'X' ball bearings have ogival grooves, making them sort of equivalent to a pair of angular contact bearings, because that's how they are used; in a single installation to resist radial loads, axial loads, and moments produced by overhung radial loads.

I think the relatively large groove radius you report is intended to make the bearing relatively insensitive to misalignment, but that of course interacts with the actual major/minor diameter of the grooves and the ball size and the parallelism of the groove center to the bearing faces.

... and I am guessing, too. I know less than what you can find in the 'engineering' section of any bearing maker's thickest catalog.




Mike Halloran
Pembroke Pines, FL, USA

 

[tbuelna]

The race surface cross section profile of ball bearings have a radius slightly larger than the mating balls. The term for this is osculation, and the race profile radius is usually defined as a percentage of the ball diameter. Most radial ball bearings use a race profile radius equal to somewhere between 0.52D and 0.55D (D = ball diameter). The inner and outer races typically use slightly different osculation ratios to balance fatigue life and efficiency. In general, there is a trade-off between efficiency and load capacity with osculation ratio of ball bearing races. A lower osculation ratio like 0.52 (ie. a more conformal contact) will give better load capacity, while a higher osculation ratio like 0.55 (ie. a less conformal contact) will give better efficiency.

The bearing described in the OP seems a bit unusual. There are single row self-aligning ball bearings, but they would typically have a much larger outer race profile radius than what the OP describes. The drawback of self-aligning ball bearings is that they have very limited load capacity, so it is more common to see two row self-aligning ball bearings.