[TheForge] bronze propeller shaft

[RIES NIEMI]

on 7/21/03 6:54 PM, John Emmerling at gearhartironwerks@direcway.com wrote:

> Hi
> I recently came by two 10' prop shafts...1.25" and 2" . anyone know what
> kind of bronze they may be? I worked a small piece under the air hammer
> and it seems to have a fairly narrow  range. suggestions would be much
> appreciated.
> thanks
> John Emmerling

There are quite a few alloys of bronze, but it is most likely to be silicon
bronze, or possibly an aluminum bronze. Could be naval bronze, but naval is
pretty soft. Naval is sort of a gold color, silicon bronze has more copper
in it- if you shine it up it often looks just like copper. Some bronzes,
particularly if they have lead in them, dont forge very well- if it crumbles
easily, its probably a lead alloy.
Most bronzes need to be worked, as you said, in a narrow range of heat- too
hot, and you have a puddle. too cold, and you get cracks. Best to do it in a
dark room, and work it just below red- sorta starting to get red, but not
quite. With naval bronze you can work it when it is sort of brown to purple.
Naval bronze is really gooshy- just flows when you hit it. Silicon bronze is
a little more forgiving, and you can actually get it up to a light red. It
is harder, more similar to working steel, with 2" you actually have to hit
it pretty hard to move it.
I havent forged any aluminum bronzes, but my friend phillip has, and he says
they are quite forgeable. He is also one of the best blacksmiths around, so
I sometimes take his "easy" with a grain of salt.
A really good reference on bronzes is the Metals Handbook, published by the
ASM. I happened to find one cheap used, but good libraries should have a
copy. It discusses the actual alloys of a hundred or so copper alloys, their
forgeability and machineability, techniques and uses.