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Here’s another “meta-project:” a DIY project that in turn makes other projects. It’s a miniature, working foundry that casts real metal parts safely on your desktop. Make custom jewelry, tiny trinkets, diecast-style game tokens — then remelt them and recast, again and again.

What makes it all possible is a special eutectic alloy, Field’s metal, which melts at an amazingly low 144°F (about the temperature of hot coffee). Unlike other low melting temperature metals, this alloy of bismuth, indium, and tin contains no lead or cadmium and is safe and nontoxic.

The basic foundry is made from wood and metal along with a few scrounged household parts. If you’re up for a challenge, you can also dress up your Desktop Foundry with some snazzy brass trim and a twirling phoenix turbine, just for fun.

The simple foundry design has a center shaft mounted vertically on a wooden base. The shaft swivels 90° to move the crucible from the heating lamp over to the mold. The cork handle swivels to tilt the crucible and pour the molten metal into the mold below. There’s also storage for molds, metal, and matches. This tiny foundry uses a thimble for a wick snuffer.

Steps

Step #1: Get the stuff!

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  • None of the materials or dimensions for this project is critical except for getting your hands on some Field’s metal. I found some for sale online through a scientific toy company. In small quantities it’s a little pricey, but you’ll only need a thimble-full or two of the stuff to have fun casting, melting, and recasting. Fun fact: It’s named for its inventor, MAKE contributor Simon Quellen Field!
  • Use Sugru, the super easy-to-use silicone rubber material, to make the molds. It comes in handy small pouches perfect for this application.
  • I pilfered an alcohol lamp from an old chemistry set. For the see-through crucible and storage vials, I used contact lens bottles but any small glass bottles will do. To make it easy to pour, use a bottle with the least “shouldered” neck.

Step #2: Build the base.

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Cut the base to size. If you like, use a router to add a decorative flourish to the edges. I used an ogee curve bit for a “desktop pen set” look. I also cut a 45°-beveled front face, but you can leave yours plain.

Step #3: Build the base (cont'd).

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Mark and drill the holes for the shaft (1"), your bottles, and your lamp. All holes are drilled 3/8" deep, so use a drill press for best results. Drill a 1/8" through-hole in the center of the recessed shaft hole. I also milled some recessed tray areas for storage of the snuffer and extra molds, although you could use a router as well.

Step #4: Build the base (cont'd).

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  • Make a mold holder about 2-1/2" high using 2×2 or any leftover wood scraps from your shop. I milled a small recess in the top to help hold the Sugru, but it’s not required. Cut some L-shaped supports as shown in the second photo, then cut bevels on the front. When glued in place in the center of the base, they’ll keep the mold holder in position while casting.
  • Cut the 1" dowel to 5" long and drill a 1/8" pilot hole in the bottom for the wood screw. Drill a series of 7/32" holes crosswise through the upper portion of the shaft for adjusting the height of the crucible. Twist the dowel 90° and drill a 1/4" hole 3/8" deep, located 1/2" from the bottom of the shaft. I added some decorative rings using a lathe.

Step #5: Build the base (cont'd).

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Cut three 1" lengths of ¼" dowel and glue one into the hole near the bottom of the shaft. Place the shaft in the center hole in the base and fasten the wood screw and washer through the bottom. Tighten the screw just snug, so the vertical shaft can rotate in the hole. Add 3 stick-on rubber feet to the bottom of the base.

Step #6: Craft the crucible.

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  • Cut a 14" length of brass wire and wrap the center around the lip of the small glass bottle. Twist the wire to make a long handle, then cinch it tight on the bottle using vise-grips.
  • Thread the twisted wire through the brass tube. Put a setscrew collar over the tube, then slide the tube through one of the 7/32" holes in the shaft. With the alcohol lamp in place, turn the shaft and slide the brass tube so that the crucible bottle is directly over the lamp’s wick. Hold the collar against the shaft and tighten the setscrew on the collar.

Step #7: Craft the crucible (cont'd).

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  • With the crucible positioned over the lamp, hold one of the 1/4" dowel pieces vertically on the base so that it touches the 1/4" dowel in the shaft. Mark that position on the base and drill a 1/4" hole 3/8" deep. Glue the second 1/4" dowel in the hole. This makes a positive stop to locate the crucible over the lamp.
  • Add the second setscrew collar on the tube and tighten it in place against the other side of the shaft. Drill a 1/4" hole in the center of a cork and twist the cork snugly onto the end of the brass tube to make an insulated handle. The crucible should swivel as you turn the cork.

Step #8: Mount the mold holder.

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  • Next, swivel the shaft 90° counterclockwise and position the mold holder underneath so that the crucible will pour directly into it. Carefully place the mold supports on either side and mark their positions on the base.
  • Also hold a small dowel next to the dowel on the shaft, mark its position and drill a 1/4" hole 3/8" deep. Glue the third 1/4" dowel in place — that will make a positive stop for the shaft in the pouring position. Glue the mold supports to the base, too.

Step #9: Finishing touches.

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  • Cut a 10" length of brass wire and wrap the center around the lip of the thimble. Using vise-grips, twist the brass wire tightly to make a handle as before.
  • Drill a 3/16" hole through a cork and thread it over the end of the twisted wires to make an insulated handle.
  • Finish the wood parts with a thin coat of dark wood stain to bring out the grain.
  • Drill some 1/16" holes in each end of the 2 small brass strips. Cut a piece of striker material from the side of a box of kitchen matches.
  • Place the striker on the base as shown and put the brass strips on each end.
  • Mark the holes, drill 1/16" pilot holes and then gently tap in the small brass brads, holding the striker material to the base with the brass strips.

Step #10: Make a mold.

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  • Find a small coin, trinket, or object you’d like to mold. I sculpted a tiny MAKE robot from a piece of styrene.
  • Spray some nonstick cooking spray onto the top of the mold holder (you don’t want the Sugru to stick to it). Open up a pack of Sugru and knead it, then form it into the mold base. Spray your object with nonstick spray as a mold release, wipe away the excess, then carefully press the object into the Sugru. Leave it in place for about 24 hours for the Sugru to firm up.
  • Carefully remove the object; you’ll have a mold with every tiny detail and surface texture reproduced in it. The Sugru will stay flexible and forgiving so you can easily unmold your cast metal shape, even with a bit of an undercut!

Step #11: Cast a part!

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  • Clean the oil from the mold, and dust it with a tiny bit of talcum powder to help the molten metal flow better. Put your mold in place on the base.
  • Place a small quantity of Field’s metal in the crucible and swing it into position. Light the lamp. Gently twist the cork handle to rock the crucible back and forth as the metal melts.
  • When ready, swivel the crucible over to the mold and twist the handle to pour the metal into the mold. Give the mold some gentle taps to help the molten metal flow into details and to release any bubbles.
  • When cooled, flex to unmold the metal part. You’ve cast a real metal treasure! You can remelt and recast again and again.

Step #12: Get fancy (optional).

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  • If you like, add some brass trim (Figure W) and a whirling phoenix turbine to make your Desktop Foundry worthy of your office or den! You can download my brass trim and phoenix design templates templates.
  • If you’re lucky enough to have a local shop with a “fiber” laser cutter you could have some brass parts laser-cut for you. But many shops will not cut brass — it’s too reflective and can damage their laser’s lens. Instead I made detailed brass parts by chemical etching. It’s similar to etching a PC board except there’s no “board.”
  • Photo-etching brass takes several steps: Print out your artwork on clear film and place it over the photosensitized brass.
  • Expose it to a light source, then remove the art and place the brass in developer. The areas covered by the black image wash away, leaving an acid-resistant pattern. Place it in ferric chloride solution to etch away the unprotected areas, leaving your brass part. I used Micro-Mark’s terrific all-in-one etching kit, which comes with complete instructions. (Watch for a future article on that!)

Step #13: Get fancy (cont'd).

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  • Trim and assemble the turbine, and mount it to the base atop a pointed wire. The rising air from the burning lamp makes the flaming phoenix spin around.
  • Attach the etched brass trim parts to the base using small brass brads. I painted the areas underneath first with flat black paint for best contrast with the shiny brass.

Conclusion

This project first appeared in MAKE Volume 36, page 100.
Bob Knetzger

Bob Knetzger

Bob Knetzger (neotoybob@yahoo.com) is an inventor/designer with 30 years of experience making fun stuff.


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