Why or who says roller jewels have to be of jewel material? Why not a metal rod soldered to the table? You could file it to fit.

Patrick,

Roller jewels are an intended to minimize sliding friction between the roller jewel and the pallet fork. A polished hard stone such as synthetic ruby will slide quite easily against hard steel, brass against steel will work, but it's important to remember that a detached lever escapement relies on brief and minimal friction for optimal performance. If you were to replace the roller jewel with a brass or steel pin, said performance would be compromised.

William

Sounds good to me. I figured there was a good reason but I didn't consider friction.

I found a balance wheel in my junk parts drawer that had a steel roller 'jewel' installed by someone. You can see from the photo that the end has some significant wear. I'm sure the performance would definitely have been compromised.

Robert,

I have seen the same thing but with a piece of brass rod in place of the jewel pin. Why would someone go through all the trouble of making a brass "pin" to fit the watch when it would have been less work to just replace the jewel ??