Reply by Kazooman

I m not sure I understand exactly what the problem is. Do you not use two wrenches to tighten it? With a wrench holding the arbor in place, it seems like the only way the nut would fail to tighten against the blade is if there is something wrong with the nut or flange.

- jonah

It’s an older contractor saw. Probably doesn’t have flats for a wrench on the arbor. Normally you can spin the nut on finger tight, and when you hold the blade there is enough friction to hold the arbor in place and you can tighten the nut further with a wrench. In the OP’s case this used to work and after mounting the Freud blade when he tries to do the final tightening while holding the blade the nut and arbor both turn and the nut doesn’t tighten up.