Subject: Re: Melting Aluminum and brass

From: [email-masked] (Rich Feldman)
Date: Thu, 26 Aug 1993 17:53:00 GMT

> From: Dave Larsen <[email-masked]>
> Subject: Melting Aluminum and brass

> I've heard that is possible to melt your own metals for small castings
> (in this case golf putter heads). I have some scrap brass (old faucets)
> and aluminum (pistons or pop cans). Someone said that you use charcoal
> and forced air. I was planning on investment casting that has been
> discussed recently.
> 
> Has anyone tried this? 

	I have cast well over 100 lbs (total) of aluminum, zinc, and (on 
one occasion) copper melted in a home-made crucible furnace.  It's a 5-gallon 
metal paint can with a 2 inch lining of fire clay and sand, and a 2 inch 
thick lid of the same material.  Construction more-or-less followed the 
Charcoal Foundry book available for about $6 from Lindsay Publications 
(see FAQ for address).

	Originally I used charcoal briquets and forced air (from an
old-style hair dryer with a corrugated air hose).  Soon I converted to 
propane 'cause it's much more convenient, just like in barbecues, but 
the author of the book made a servicable metal lathe and milling machine 
with aluminum castings from a charcoal-fired furnace.

> Is there an easy/cheap way to try it out? 

	To heat a crucible big enough for your golf putter heads
(say, about 2" diam and 3.5" high) you can just stack up some bricks 
or concrete blocks, with a square cavity 2 briquets wider than the 
crucible.  Have a steel grille 1 brick above ground level, with the 
ability to blow air under it with a fan.  A little fancier would be
to line it with a coffee can or paint can surrounded by sand, dirt, 
or mortar of some sort.  

	The furnace should match the crucible (not too big).

> What do you use for a crucible? 

	For an inexpensive start I would recommend the bottom 4 inches
of a 14 ounce skinny propane cylinder.  This is seamless steel and much 
thicker than a soup can or oil filter.  If the separate base piece
comes unbrazed and falls off, you won't be able to set the crucible on
a level surface without it tipping over.  Punch two holes near the top 
edge for a wire bail like that on a bucket.  That can be made from a 
coat hanger, with the ends hooked so you can engage the crucible from 
the inside after it is hot and ready to pour (tip it with pliers).  

	Inspect it after each melt for signs of burning through.
It's soft when hot, so be very careful not to poke through the bottom 
when stirring your melt.

A cast-iron saucepan would do for a larger-scale project.

	Nowadays I use a real silicon carbide crucible for Al.
Also use a steel pot made by welding a disk to the end of a short piece
of 4.5 inch pipe.  Once melted 1/2 gallon of pot metal in a 1 gallon steel 
paint can (not recommended!) over charcoal in a stack of concrete blocks.
A propane-cylinder end once failed as I lifted out the third melt of 
pure copper.

	I think a soup can would suffice for an experimental pot-metal
casting, maybe even aluminum.  Always be protected to prevent burns if 
your entire melt spills at your feet, or splashes in the direction of your 
hands or face.

> Are these scraps suitable  (is there something I should know that I
> don't)?

	Practice with aluminum (or pot metal, e.g. carburetors and 
window cranks) before you try to pour brass.  IMO the specific gravity 
of Al is kind of low for putter heads.

	Don't mix different kinds of scrap, because of incompatible 
alloying elements.  Cast scrap is generally better than wrought scrap,
because you know the material has good casting properties. If you use 
beer cans, pound them as compact as you can before heating, and be
prepared to scoop out infusible dross which will exceed the volume of 
molten Al at the bottom.

> Any source of information would be appreciated. 

	Read some books (get the Lindsay catalog).  I would recommend 
you try green-sand molding before investment casting... dimensional 
accuracy and surface finish may be OK for your putters.  Investment 
molds (especially plaster-of-paris) need to be baked good and hot to 
be sure there is no moisture to make the metal pop back out.
You may be able to make a 2-piece plaster mold around a hard 
pattern, without bothering with wax.  

> Thanks:
> Dave
> [email-masked]

any time.  Anybody want some nice professional molding sand
for $0.10 per pound + shipping? (I have a few 100 lbs more than
i'll be needing in this lifetime).
-Rich
-- 

Rich Feldman		Megatest Corp., San Jose, CA 95131
[email-masked]  	{decwrl,sun}!megatest!rich
home (415) 967-6966	work (408) 441-3027