wrote in message
oups.com...
Making a custom brass instrument?

This actually is correct -- good guess. As I've mentioned, I'm an
absolute novice, so I'm not suprised I didn't supply enough
information; I'll try to be a bit more specific -- here is what I'm
trying to replicate or at least get something similar to:

http://devnull.dtcc.edu/gfx/brass.jpg

The body (lower part is 1/2" pipe) and the top part where it's most
wide is 3/4" -- I don't think it's a conventional brass fitting or
adapter, so I'm assuming it was either manufactured or somehow tapered
into that shape. Hopefully this is a bit more information and the
photograph will help.

Thanks for the advice and patience!

Rob

Machining that part would entail starting with stock thick enough to form
the larger OD (outside dia), then removing metal both externally and
internally to form the tapers and possibly the bore diameter. If the inside
can be a straight bore rather than internally tapered, this is probably
easiest -- though the resulting part might be a bit heavy and I've no idea
how it would perform musically.

If I were making 25 or more of these, I would make an expanding mandrel so
they could be made from 1/2" tube. In your case, have a machineshop make
the mandrel. The mandrel would have several segments and possibly an
extractable central cylinder so it could be removed once the shape is
formed. I would anneal the tube, insert the mandrel, chuck the lot up
in about any lathe, and apply a roller to the metal while expanding the
mandrel. The action of the roller pressing the tube wall against the
mandrel (with some force) will gradually stretch the metal to shape.
Then collapse the mandrel, pull out the center and then the segments from
the finished workpiece, and so on.

I think the workpieces would only take a very few minutes to make, once you
had the mandrel.