Lee Schierer in McKean, PA
Most table saws use an an Acme thread on the arbor. They will not accept a regular threaded nut. The first step should be to replace the current nut. Tighten the new nut snugly using a wrench. Run the saw and see if the new nut works better. If your new nut is binding when fully tight, add one or two thick washers between the nut and the flange to move off the worn thread area of the arbor.