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How to Make a Speed Control for a Wood Lathe

A dimmer can be adapted to control a lathe's speed.
lathe image by Tomasz Plawski from Fotolia.com

A wood lathe is a rotary motor tool that spins a piece of wood or metal so that cuts can be made around the entire circumference of the piece to form it and create patterns. The machine commonly is used to make stair railing spindles and furniture legs. While some lathes have built in speed control, many well-built, less expensive tools do not. Using a dimmer switch for lights allows you to adjust the speed of lathes that do not have speed control.

Things You'll Need:

  • Junction Box
  • Lineman'S Pliers
  • Heavy Duty Extension Cord
  • Dimmer Switch
  • Wire Stripper
  • Screwdriver
  • Utility Knife

Cut a heavy duty extension cord in two using lineman's pliers. Make the male end long enough to reach the nearest electrical outlet. Leave the remainder attached to the female end. Use a cord that is the correct length to provide power to your lathe without a lot of excess cord that will cause a safety hazard in your shop.

Strip the casing back about three inches on both of the extension cord pieces. This will expose three individual wires on each cord segment. The casing can be stripped by cutting lightly into it with a utility knife and pulling it off with your fingers.

Strip the insulation from each wire using a wire stripping tool approximately 1 inch from each end. Place the wire in the hole on the stripper that most closely fits the size of the wire and pull.

Thread the three wires of the extension cord with the male connector through the top hole of a single-switch plastic junction box.

Loosen the top two screws on the dimmer switch and the bottom one, which will be green in color to signify ground. Twist the strands of your three wires clockwise to create smooth ends. Wrap the end of the black wire around the screw with the plus mark and tighten it with a screwdriver. Wrap the white wire around the screw with the minus sign and tighten it. Wrap the green wire around the green screw and tighten.

Thread the three wires of the cord with the female connector through the bottom hole in the junction box. Attach them to the lower screws of the switch as for the top, black to plus, white to minus and green to green.

Pull the knob of the dimmer up firmly to remove it. Install the dimmer switch cover by slipping it over the spindle of the switch and threading the two mounting screws through the plate into the screw sockets in the junction box. Tighten them with a screwdriver.

Replace the knob and turn the dimmer to the off position. Plug the cord into the power and connect the female end to the power cord of your lathe. Turn the power on to the lathe. Twist the knob of the dimmer slowly to the right to increase the voltage, thereby increasing the speed of the lathe.


Mount the dimmer to a nearby wall for easy access.


  • Blow the dust from the dimmer periodically to prevent overheating.
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