Posted by AL.H on March 01, 2000 at 23:41:16:
In Reply to: Bell repair & "spinning" posted by Dale Phelps on March 01, 2000 at 21:45:03:
On bell spinning-
A nearly finished bell 'blank' is secured to the outside of a form and then pressed on to that form to give it its perfect final shape. If you don't have that mandrel form, then spinning would be just about impossible. You have to have a solid backing to press against. For a repair, an experienced guy with good hands can push any shape of bell back into place real close by eye with a roller dent machine. SO, if you want to make a replacement bell or some custom job, then you would first have to MAKE a mandrel. On a lathe big enough to swing a ?? inch bell! Then you would have to get the sheet brass seamed and formed up to be a close fit on the mandrel. I believe some tuba bells are spun on a "lathe" with a vertical spindle. ( A proper production mandrel would probably be steel and require a chain hoist just to move it.) Developing this kind of tooling and machinery is part of what we pay for with these nice new tubas. A "one-off" job is just not practical.
Maybe a REALLY good repairist could freehand a custom bell just on the dent machine, but I'm not sure what kind bead could be made.