Many will know ballraces come with different internal clearance depending on intended usage. eg CN = normal, for a transition or very slight interference fit on either inner or outer race. For a bearing pressed into a housing / onto a shaft, C3 clearance would be used. C5 is the highest standard clearance, designed for where both inner and outer races are a press fit.
Now, one-way bearings (sprag clutches) need to be able to transmit torque, and therefore are expected to be a press fit on both races. Needless to say, this would require a C5 bearing - and that's how I understood one-way bearings were supplied. But I just found out differently.......
Last weekend I pressed sprag clutches into the starter I'm developing for my GF. Interference was in line with specified n6 fit but, to my dismay, the shaft could not be turned by hand once assembled. Upon disassembly again, one bearing seems OK but the other feels as if it has a cracked ball inside. Naturally, I enquired of the supplier what clearance his bearings had, and was alarmed to hear - CN. No wonder they failed.
But here's the rub - I enquired of other one-way bearing suppliers as to what clearance their products had, and all said - CN. Summat wrong here. I'm suspecting all these people are getting their supplies from the same Chinese supplier; one who doesn't understand clearance / fits in the same way heat-treatment is not always satisfactory over there.
Which leaves me with a query - where to get sprags with the proper clearance? Catalogues list these bearings as clearance C5, but getting any is proving elusive.
