340 rings

You have to be careful not to raise a burr when you do that so you don't score the crank...

A burr in the front side will score the crank, a burr on the back side will make the bearing tight and cause more resistance for the crank to turn or even lock the crank up...

It doesn't take much for a bearing to get tight, I've seen a small speck of dust or string from a cotton glove lock up a crank due to the interference it causes with the bearing on the front or back...

It's best to get them from the manufacturer...
Absolutely agree. I did this with the precision of a surgeon using needle files. Always stroked away from the inner side, and cleaned up the back side when I was done. It took me a while that's for sure.