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How to Make a Trommel for Gemstones

A trommel is a device used for sifting a variety of materials such as gemstones, gold or garden mulch, sorting them into several sizes. The trommel is primarily a cylinder that turns slowly allowing the various materials to fall away through mesh walls into a container. Rock hounds and other collectors can make a homemade trommel with a few easy-to-gather materials for separating gemstones from surrounding earth.

Things You'll Need

55 gallon drum
2 bicycle rims
1/4 inch wire mesh
Drill
Jigsaw
Safety goggles
32 flat head bolts with nuts, 1/2 inch long
Staple gun
Crank
4 caster wheels
Old table
Metal cabinet drawer pull
Tarp or empty bin
Wood screws

Instructions

- 1
  Measure the diameter of your drum. Using the jigsaw, carefully cut out one end of the drum, leaving its rim intact. Set aside.
- 2
  Measure to make sure your two bicycle rims are the same size as the diameter of the drum.
- 3
  Lay the drum on its side and attach the two bicycle rims, one on either end. Drill through each bicycle rim and the edge of the drum, attaching the bolts and nuts every 2 inches around the bicycle rims. Do this on both ends of the barrel. The bottom of the drum should still be attached.
- 4
  Drill a hole on one side of the barrel. Using that as a starting point, cut a 1-foot by 2-foot rectangular hole with the jigsaw in the center of the side of the drum. Make a similar hole in the center of the opposite side of the drum.
- 5
  Cut 2 pieces of wire mesh, each being 1 1/2 feet wide and 2 feet long. Attach the wire mesh to each rectangular hole from inside the barrel using the staple gun. If your drum is smaller, cut the side holes and the mesh to correspond to the size of the drum.
- 6
  Purchase casters that will fit the inside of the bicycle rims. Attach the casters to the table in positions that will correspond to the width of the bicycle rims. Drill holes in the table to attach the casters with screws. The barrel should be able to lie on its side with the rims resting securely on the casters. Screw the casters to the table close enough to support the drum but not allowing it to touch the table.
- 7
  Drill a hole in the center of the bottom of the drum and insert a screw to attach to the crank. Use whatever size crank works well for you and the size of your drum. Attach the crank assembly to the outside of the bottom of the drum.
- 8
  Attach the metal drawer pull to the center of one side of the end piece you removed earlier to make a lid. After the trommel is filled with dirt, attach the end of the drum by sliding it into the hole at the end where you initially removed it.
- 9
  Cut a 2-foot square hole in the table between the positions of the casters. Lay the drum assembly on its side so the bicycle rims rest on the casters. The mesh-covered holes in the drum should revolve over the hole in the table.
- 10
  Fill the trommel with dirt and gemstones through the top of the drum. Close the lid and rotate the drum by turning the crank. Place a bin or tarp under the table to catch debris as it falls out of the barrel.

Gemology