I am restoring a 1972 PX-10 and the rear wheel has a bent axle. I have found a suitable replacement and will be reassembling soon. The cones and locknuts were all removed from the bent axle to put on the new axle. Do I just center the axle in the wheel by eyesight or do I need to measure or count threads to make sure the axle gets centered?

Counting them won't hurt. If it's a quick release (QR for short) axle, you mustn't have axle protruding beyond the dropout on either side, otherwise the clamping action will be compromised. Its a bit fiddly to set up, but you can get the centering correct with everything assembled finger tight - then lock down one side before adjusting from the other side. Remember to allow for the axle compression imposed by the QR - this means a properly adjusted bearing has a little slack before the QR is clamped. Otherwise it will be too tight on the bike.

It sounds like a nice project

Cheers,

Ed

I always eyeball. Too lazy to count.