Some have [one screw ] While others have a rivet in chassis [ just above the 1975 date on plastic base insert] Use a small pilot drill , then larger one to drill off rivet head. Never seen a treaded pin. In theory should be able to leaver off? or this may be a refix job . Treaded pin may have been used like a self tapper try un screwing it? Refixing super glue, self tapping screw [ either large one or small with washer. Watch out as each axel has two small springs easily lost. If the springs are [ not springing ] you can try stretching them. I have used old biro pen springs which need to be cut in half. Cheers Jim