A few weeks back, I posted a teaser about doing some home foundry work. 40 some years ago I worked in a foundry for a few months, (before I got smart and moved on) so I had a bit of knowledge about what I needed to do to cast some aluminum parts for my truck.
First I drew out the design I had in mind, there were several tries before I had a design that could be cast easily and had the "look" I was after.
After the drawing was complete, I started by making the pattern. I chose to make what is called a matchplate pattern. 1/2 of the pattern is fastened to each side of the base plate. The white piece was split, doweled and screwed together before machining.
I also made the mold flask that would hold the sand. Sorry no picture!
Next I needed a furnace to melt the aluminum. After looking over the options I decided coal would be the simplest for a beginner. Waste oil would need a burner, as would LP gas and I didn't want the learning curve of building a functional burner when I only planned to make a few parts. Coal is simple, I had a junk Oxygen bottle so I cut that in two and used the top half to house my coal fire. The valve was removed and an airline was plumbed up, then this was surrounded by sand, standing in a garbage can.
I welded up a crucible from 6" pipe and a piece of 1/4" plate, welded on some ears to lift it and a place to hook on for tipping/pouring.
I also made the necessary utensils for stirring, skimming and pouring, all from rebar. This was all stuff I had laying around, so I haven't spent a dime on the furnace.
I read up on foundry sand and with the help of a casting forum acquaintance came up with some bentonite clay and that along with a few bags of silica sand from the building supply store, (and a bit of water) gave me foundry sand.
The way I chose to build my pattern, a core would be needed to form the inside of the cup. I made a pattern the shape of the inside, then made a fiberglass mold from that, this I could fill with a mixture of silica sand and polyester resin. (fiberglass resin) After the resin hardened I had a core for my mold.
The actual making of the sand molds was easy for me, as that had been my job at the foundry all those years ago.
After a bit of trial and error, I got my coal lit and some aluminum melted, made a pour and the first part came out almost perfect. 2-3lb coffee cans of stoker coal would melt enough aluminum to pour 3 molds. With only one flask, I had to hustle building molds in between pours. This is the better part of 2 days of work, I think to get this many parts, I had 5 failures. for some reason the larger parts were more temperamental and none were perfect, but by making subtle changes in the finished part shape I have 2 of the 3 that can be made to work
This much of the project was done last May, but I deliberately waited until now to do the clean up and machining of the castings. (cold weather, warm basement) I had to make soft top jaws for my little South Bend lathe to hold the castings. I don't own a mill, so these were made on a table saw with a carbide tipped wood cutting blade. Because I knew I couldn't make them perfect, I bolted them on the chuck, then bored the work holding surfaces true. They might not be the best jaws, but they work for what I need, as far as tolerances.
I got the first one finished tonight.
The only differences between the gauge cup and the clearance light cup is in the diameter of the inner bore. Both the gauge and the light will be held in with a bolt from the rear.
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“He, who is without oil, shall throw the first rod” Compressions 8.7:1
Steve Peterson
Central Wisconsin
Follow The Leaders For They Know The Way AUTOCAR