A new capability, metal casting.

[Ed/KB1HYS]

Well, I built a small foundry (1 gallon can size). Charcoal fired, I originally tried it propane, I had no regulator and the torch burner was too small to get enough heat. Charcoal is cheap and effective and a lot safer.

 I was able to make a test pour of about 12 oz. of scrap and produce a very good ingot of clean aluminum (about a 1/4 to half cup size). This is the volume limit now pending a slightly larger version.

So, I was thinking of casting some hard to get parts. Probably investment casting using molds made from either a broken sample or something easy to make a pattern of.   Nothing to complicated, yet.

Any idea's or requests? 

 I CANNOT guarantee that any of these castings would turn out ok (it took me 3 tries to make an acceptable ingot, let alone something more complicated).  But I'd like to try my hand at making something useful needed.

[KA2DZT]

Making a mold is the hard part.  Usually, if you can make a mold using machines, you can instead just make the part itself.

What parts do you think need to be made??  For radios, xmtrs??  It's rare that those type of parts break (castings).  Castings usually need follow up machining, flat surfaces, holes, etc.

Fred

[Ed/KB1HYS]

I'm not sure about what the parts would be.  I have seen certain pot metal parts (Zenith Band switch arms come to mind) that break easily with age, or decay or corrode away over time. etc.  

You're probably right, most things could more easily be replaced by simply manufacturing a replacement out of some other parts.  I would probably use the damaged original to make a lost wax mold. This process produces a nearly exact replica of the original part.  The original piece is surrounded by a rubber molding mixture, cut out, and that mold is used to make a wax copy.  The wax copy is then surrounded in plaster, once the plaster cures, the wax is melted out, leaving a very good female mold.  The molten metal is poured in, and then once it is solid, the plaster is broken away. A little finishing machining is always required, to remove the parts that allow for the molten metal to be poured in and vents etc.

I just thought I'd put it out there, figuring if someone had broken something "unobtainium" I would make a try to make them a part.

For my own use, I have parts in mind to be made using the lost foam technique, which does produce a nice surface quality casting and a bit easier than lost wax.

[Opcom]

you could always make toy soldiers. Can't get the metal ones any more..

[kb3ouk]

got any pictures of it? i'd like to see what this forge looks like.
shelby

[Ed/KB1HYS]

I'll get some pics. Very simple construction. 

1-gallon sized tin can (coffee can) 
1-quart high performance Sheet rock spackle (contains mica and other minerals besides gypsum)
1-2 gallon bag of perlite (garden store variety)
some sand.

Mix it up, and cast it inside the can as a liner.  Let harden for a day or two. Punch a hole or two near the bottom for forced air inlet and done.   Fire up slowly the first time to really dry out the refractory mix. 

So far I've done lead and aluminum melts and the outer can skin hasn't even become discolored. It did get pretty hot to the touch, but the real heat stayed inside.

I think the toy solder idea is a good one!  I can get used Tire weights for nada and they would be a perfect source material (free). Though I wonder if they are antimony now instead of lead?

And yes, I will be wearing a respirator when working with the lead and zinc.

[Opcom]

I got the toy soldier idea looking at casting on wikipedia. They show the mold in detail as well.

So what are you using for the tue on that furnace?

[KC4ALF]

I use the lost wax for reproducing parts when restoring cannon and implements. I save Charcol for tempering springs  and hardening. Bituminus coal, coked produces a fine smelting heat and is readily available here. My forge was made in the 1890's and uses the original hand cranked blower.

Good luck.

[KC9LKE]

Ed:

Just an FYI there is a metalworking board call “the home machinist”. A Google for that or Chaski should turn up something. Very knowledgeable and helpful group, like this board.

Yes rolling your own is very rewarding. Now you need a small lathe and a mill. 

Best of luck with your new capability.

Ted / KC9LKE 

[KA3ZLR]

Hi,

And Lots of initial expense, but it can be rewarding.


73
Jack
KA3ZLR

[Ed/KB1HYS]

I wish I had a Lathe and/or mill.   I'd have myself a nice running steam engine producing power right now!!   

When you say Tue do you mean tuyeres?  The air inlet is cast into the refractory material, just a circular opening. I place a small blower with a .500 inch tube about 6 inches away to throttle the airflow. Work good, and can REALLy throw some sparks if you crank too much air inthere.

[N4LTA]

I built and electric one several years ago and melted down lots of Al scrap. Poured it into steel muffin tins to make nice ingots for storage.

I never made a decent mold though. That is the difficult part. I cast a couple of bars and turned them in the lathe but the cast metal quality was just so so.

[W1AEX]

Ed,

I'm always amazed at the resourceful nature of many hams. It looks like a very useful project, especially in a hobby where we work with equipment that can be prone to mechanical failures as often as electrical failures. Hey, if western civilization crumbles, your work may lead us right out of the dark ages!

Rob W1AEX

[Ed/KB1HYS]

Ok for the one who asked for pictures.  Shown is the furnace (can thing) gloves, tongs (long needle nose), 3 crucibles(one tin can and two steel) the largest is a cut down propane cylinder, You can see a bit of aluminum in there waiting to be melted.
Enough charcoal (real charcoal) to melt about a lb of aluminum and a small Muffin top ingot of leftover melt from last time. The blower for feeding the fire and of course, some heavy gloves.   I wish I had a pic of the fire going, it is impressive for such a small size furnace.  There's a cover for the furnace too, but not here.

Total cost for the capability, including fuel was less than $20.

[Opcom]

I wish I had a Lathe and/or mill.   I'd have myself a nice running steam engine producing power right now!!   

When you say Tue do you mean tuyeres?  The air inlet is cast into the refractory material, just a circular opening. I place a small blower with a .500 inch tube about 6 inches away to throttle the airflow. Work good, and can REALLy throw some sparks if you crank too much air inthere.

Yes exactly what I was asking. I like that sort of thing, don't have time for it except to read, but am interested in seeing it.

[KM1H]

What is needed for source aluminum? Cast, sheet, mixed, or what? What about alloys? Old aluminum heads and injector manifolds from a boneyard would be source for cast.

[Ed/KB1HYS]

Right now I'm using any scrap aluminum available.  mostly a lot of bits and pieces left over from various other projects, and any bits of scrap I can pull out of the heap.  I tried crushing cans and using them but the amount of contamination from the coatings made that tough.  I don't worry about the actual metalurgy invovled as none of the castings are intended for structural or 'life support' applications    

I do try determine if I'm melting zinc or zinc alloys as the fumes can make you ill.   

[KA2QFX]

You might want to get in touch with "Jackson" Bob K1REC about making molds and investment casting. It what he does. 

If you need access to a machine shop and care to drive up to Concord you're welcome most anytime.http://home.comcast.net/~msed01/shop.html

I know where there is currently a complete home machine shop available.  Small lathe, long bed. Really nice small knee mill, loads of fixtures and tooling. The guy was a master machinist by trade and a gunsmith at home.  PM me if you'd like more info. 

Mark