3/8" diameter vs 5/8" diameter?

Question

I have two older windows, that I believe are Am Craftsman windows with one broken spiral balance each.  I want to order replacements, but I have one measurement concern.  After carefully measuring the existing balances, the OD measures 1/2" to the best of my ability to resolve without removing one (which is probably what I should have done - shore house) - my concern is using a 9/16 - 5/8 balance and whether it will fit into the space for the balance.  I could use a 3/8 balance, but is the anchoring hole at the top significantly smaller than what is used on the 5/8 balance?

Tom · Accepted Answer

There is a big difference between a 5/8" and 3/8" balance, and they are very rarely interchangeable. It's not a matter of the anchoring hole but more a matter of the strength of the balances. A 3/8" balance is very skinny and will likely not be able to hold up the weight of a window meant to work with a 5/8" balance. I highly recommend getting as accurate a measurement of your spiral balance's tube diameter as possible.