I am working on my friends 21J 60Hr Bunn Special. After cleaning and partial assembly the free spin test was done. Came to find out the mainspring barrel is catching on the third wheel. The upper mainspring barrel hole is so enlarged towards the center of the movement that the barrel rocks excessively. Since it has a motor barrel the hole is large it’s over 5mm. How can the hole be made smaller?

Thank you,
RR

If you have the tools you can clean up the hole (Make it round again) or drill it out. Maybe a diamond ream would work. Get a clock bushing, measure it and make it fit the hole, then press it in with your staking set tools. Be sure it does not protrude on one side or the other and interfere with another part. Maybe you could find a bridge bushing, say from a old 18s and use it.