How to Build an Arc Furnace Welder

Drill two holes opposite each other, just below the lip, in the 2-inch pot. The holes need to be just large enough for the carbon arc-light rods to fit through and be snug. File off any residual terra cotta flakes.

Cover the hole in the bottom of the 6-inch pot using a piece of duct tape. Fill the larger flowerpot with sand to about 1 inch below the outer lip. Pack the sand tight. Set the 2-inch flowerpot centered on the packed sand. The top of the small flowerpot should come to roughly 1 inch below the top of the large pot. Fill sand around the 2-inch flowerpot to just below the holes.

Drill one hole in the side of the 6-inch flowerpot that lines up with the holes in the 2-inch pot.
Slide one of the carbon arc-light rods through the two pots to mark where it hits on the opposite, inside flowerpot wall. Drill a hole at the mark and slide one light-rod through each side so that they meet in the center of the 2-inch pot.

Pour sand around the 2-inch pot to meet the level of the rod. Settle this level of sand by pouring a little water on it, but do not saturate the sand. Pack fire clay around the two rod pieces that are on the outer sides of the 2-inch pot. Make sure the fire clay is firm but that the rod slides through freely. The fire clay must also be flush tight with the inside of the 6-inch flowerpot walls. Pour sand so that it's level with the top of the small flowerpot; settle the sand with a little bit of water. Withdraw the rods and set the arc furnace aside to dry for 24 hours. Cover with the saucer from the large flowerpot.

Prepare the carbon light-rods by clamping a brass clip about 2 inches from each of the outer ends. These clips help furnish a good electrical contact. Tape a 2-inch piece of glass tubing to one rod, using electrical tape. This glass tubing will help you make future adjustments. Do not handle rods without gloves while in operation. The opposite rod should be held rigid and straight while operating. To start, touch the carbon rods together.