Probably on the smaller range, like 0.0005 to 0.001 for the size of bearings we deal with. 2 thousandths on 2 inch diameter is true interference fit. Bearings want to be a bit less than that.
Knurling is a common dodge for those whose inner races/roller turn.
Heh. 1978 Isuzu/Chevrolet LUV Truck. Started making a "scree-scree" noise about 4 months after the one year manufacturer's warranty ran out. I brought it over to my friend and Shop Superintendant Fred Baldelli at the Westboro, MA Chevy garage. He came back with the diagnosis that the front wheel spindles were shot (?) likely defective from the beginning, and that I was looking at 3 weeks minimum to get replacements from Japan.
I NEEDED that truck to get back and forth to work.
"Fred, are the spindles blue?"
"No."
"Could we knurl them and increase the interference between the spindle and the bearing inner race?"
"We could if we had a portable knurl. But the shop doesn't have a portable knurl."
"Oh yes you do" my reply.
I went over to Fred's toolbox, grabbed out a pair of stout vise-grips, adjusted the setting, and then with all the hand strength I could gather clamped them over the spindle, upsetting the metal and creating grooves/ersatz knurls.
The inner race now required a punch to get it on over the knurls, but once in place - it wasn't moving.
Fred did recommend I replace the spindles as soon as I could. I drove the truck for another two years after that before I traded it in on a better car. I guess that constitutes a "replacement?"
Sorry. A story from my mechanic formative years.
Joe K
