Steve W. wrote:
Ed Huntress wrote:

I use the oddball stuff for items where the strength isn't a real
issue, Decorative stuff or covers and such.
The high silicon gets used for wear related items. I like using it
for castings that will end up handling abrasive abuse or in
locations where it will be the wear surface. Yes it can be a real
PIA to machine but it wears real well once finished.

It makes REALLY nice bullet molds.

I use various molds, sand, metal, lost wax/plaster. Two home built
furnaces. One is electric and one gas. The electric is NICE for temp
control and even heating. The gas is much faster to full heat but
hard on alloys.

I'd like to get into it some more, and I'm half-equipped, thanks to
the generosity of onr of our regulars here. Now I have to build a
furnace. I built one of those little Gingery charcoal furnaces around
20 years ago, and it was enough to get me interested, but it
deteriorated and I haven't replaced it yet with something better.

Soon...


I started with a charcoal unit. They work BUT the temperature control
is REALLY difficult to do with repeatable results.
The gas units work pretty well IF you have a source of low priced gas
to feed them. These days that can be difficult if you don't have a NG
line already.

This was the basic idea I used for my electric.

http://www.dansworkshop.com/2008/03/...ing-furnace-2/

Mine is larger than this and has better temperature controls (from an
industrial oven with three temperature sensors)

From a cold start I can have a batch ready to pour in about an 1.5
hours. The batches after that take about 30-45 minutes after loading.

The gas unit takes about 45 minutes from a cold start and 20 or so for
each additional batch. But you don't have the thermal control over the
melt.

I would expect you could get better control of a gas fired unit by
adding a hi low fire unit controlled by a temperature controller. It's
fairly common for certain applications such as glass melting furnaces
and I built a gas fired glass annealing oven with one for a friend which
held around 500C. Basically for the annealer a burner that can run at
low or high output and a solenoid to turn on the high output when the
temperature dropped or the ramp rate needed to be higher. For the
annealing oven the burner was an inspirator so only the gas was
controlled. The low and high end each had a gas control valve to control
the heat output, the low always being on, and the high kicking in when
the solenoid was energised by the temperature controller.