Electric Coil Winding Jig

I built this simple, cheap electric lathe for winding secondary coils. The power plant is a 120V ice cream maker I picked up at a yard sale for next to nothing. It has a high-torque gear motor that runs at about 60rpm no-load. I built a stiff C-rail from three 2x4 boards screwed & glued together. I made the C-rail long enough to accommodate coil forms up to 48" long. I stuck the ice cream maker base to the C-rail with clear silicone adhesive, and strapped it down tightly with several wraps of duct tape. The axle is a 1/2" wooden dowel. It is coupled to the output shaft of the ice cream maker with a short stub of 1/2" rubber heater hose and ring clamps.

The axle supports are made from bits of 2x4 and 1x4 lumber. I cut plywood disks for a snug fit in the ends of a 4" PVC pipe. I could easily cut additional disks for whatever size pipe I happen to be using. The 10A variac in the picture controls the RPM of the ice cream maker. I can throttle it back to a slow crawl if I wish. Don't try this with a solid-state dimmer switch--it doesn't work! I mounted the spool of wire on a vertical axle on a portable work bench behind me, and guided the wire onto the slowly rotating form by hand. A pair of clean cotton work gloves is practically mandatory for this task. One neat thing about the ice cream maker--the motor is designed to be "stalled" by an excessive load, and is not harmed by being brought to a full stop (like when the ice cream gets hard!). If I overlap a turn, or get space between turns, or otherwise need a break, I simply grab the rotating form to stop it. I can hold it still indefinitely without cooking the motor. When I'm ready to start winding again, I simply let go.

The green secondary on the lathe is the first ever wound on this jig. It is 4" x 20" wound for 18" with 1300 turns of 28AWG. Isn't it pretty? It was real easy too, thanks to the lathe. After the wire was all on and anchored at the ends with spots of hot glue, I coated it with oil-based clear gloss urethane varnish. I dunked the brush in varnish, and simply held it against the rotating coil. The varnish went on smooth as glass. After the coat was applied, I let the coil rotate until the varnish was tacky, eliminating the possibility of any runs or drips.

Think you don't need a winding jig? Think again. Even if you only wind one Tesla coil in your entire life, a winding jig is worth the bother. Two hours and $20 spent throwing a winding gadget together will save you countless hours of frustration and will keep you from making a bird's nest out of an expensive spool of magnet wire. I'm not kidding--winding a coil by hand is a miserable experience that is likely to end in dissatisfaction or outright failure. Build a jig and save your sanity. The finished coil will look better and perform better too.