My 25 year old washing machine has worked perfectly for years but has just thrown the belt. On inspection the large wheel (pulley) has loosened. I can tighten its nut but the head of the shaft that the nut and pulley are mounted on seems to slip, so the nut never tightens completely. So when I try to tighten it then run the washer the nut loosens and throws the belt again. How do I tighten the lock the nut?

Tokoh, February 2010