Harmonic balancer

Normally they don't have threads. They normally have a guide pin or lock pin. Basically a cut down the side that the pin on the crankshaft will only slide on one way. The the crankshaft snout has the threads in the center of it for the bolt to go on and it holds the balancer to the shaft.

Maybe get a picture of what you are talking about if this doesn't see to be what you are saying. Thanks

https://www.2carpros.com/articles/how-a-harmonic-balancer-works