What I have done is to get some water boiling and dip the tenon into it for a little. you will know when its soft enough to work with. Use a drill bit-not the cutting end but the other end. What I do is to run the sharp end into a block of wood and then slowly push the blunt end into the tenon hole. The tenon MUST be hot and pliable. Also this MUST be done slowly and checked so as not to go too far to the point the tenon is now way to tight as far as fit into the mortise.