I don't think that application of heat is a good idea. You stated you can't
visibly see any distortion. Are you sure the resistance is caused by the
shaft and not in another part of the bobbin assy.? What type of metal is the
shaft? You might want to speak with someone who is familiar with restoring
old sewing machines.

-Tom

"Jason" wrote in message
oups.com...
I picked up a 1951 Singer Featherweight sewing machine recently. It's
in great shape, except that even after applying lots of oil, the shaft
which rotates the bobbin assembly resists rotating through about half
its travel. Presumably this means the shaft is very slightly bent,
although I can't detect any distortion visibly. So, while I can still
turn it by hand, the motor isn't quite up to the task. Here's a photo;