Whenever I mount a full (3/4") dado set on my saw the arbor nut only goes on about half way. Apparently one time I overtightened the nut and distorted the threads slightly on the arbor shaft because now the nut no longer spins freely but I must use the wrenches to screw it on. Can almost do it with my fingers but not quite. Examination of the arbor threads looks like they are slightly "distressed". Mostly annoying!! Might buy a new nut and see if it helps. The RH arbor flange washer appears to be fixed on the shaft and I use the identical PM flange washer against the dado set for even pressure on the left. Am I missing something or does PM not intend the 66 to take full dado set?