The expander cone nut on my old Modolo quill stem was seized, and i couldn't remove it by hitting the head of the bolt with a hammer or mallet because it was deeply recessed and (horrors) it's made of aluminum. So, if I hammered on it with a drift pin, it would be ruined. So, I devised a tool made from a steel hex head bolt, by cutting off the head and cutting a slot in the end so that I could thread it into the expander nut with a long slotted screwdriver. I then hit the bolt with a steel drift pin and hammer, which dislodged the seized expander nut, allowing the stem to be removed. I did need to run a tap through the aluminum expander nut threads, which had gotten a bit boogered up during the hammering session. Just another one of those interesting problems one encounters working on vintage bikes.