How to Cut Through a Thick Metal Electrical Box

By Chris Deziel

Cutting through metal isn't as easy as cutting through wood, but there is a wide selection of tools that will do it. That selection narrows when the metal is thick, though; and when you're working in a confined space, such as you're likely to be when cutting through an electrical box, the selection narrows further to a choice of two: a drill or a rotary tool fitted with a metal-cutting wheel. Because a rotary tool is smaller and easier to handle than a drill, and it develops more rotational speed, it's the better choice.

List of Items Needed

  • Pencil
  • Ruler
  • Handheld cutting tool with metal cut-off wheel accessory
  • Safety goggles
  • Respirator mask
  1. Turn off the power to the electrical box if there are wires inside. Push the wires to the side of the box opposite the one you are cutting through.

  2. Mark the lines for your cut with a ruler and a pencil. If you are cutting a hole, trace a circle on the box. Draw a square around it with each line of the square touching the circle if the circle is less than 3/4 inches in diameter. A handheld power cutter won't cut close curves, so you'll have to cut out a squared hole. You'll probably be able to cut larger-diameter holes without tracing a square.

  3. Hold the handheld cutting tool with both hands and line up the cutting wheel with one of the lines or the circle you marked on the electrical box. Turn on the machine, set the speed to about three-quarters and lower the cutting wheel onto the line. Push gently as it begins to cut, but don't force it. Let the cutter do most of the work.

  4. Move the cutting wheel along the line after it has cut through the metal. If you're cutting a circle, rotate the tool as needed as you move around it, stopping and repositioning it if necessary. If you're cutting a line, cut about 1/4 inch past the end of the line on both ends. Cut out a square by cutting the other three lines in the same way that you cut the first one.

Tips and Warnings

  • If the box is thick or you have many cuts to make, the cutting wheel will gradually wear out. Replace it by unscrewing the screw, lifting off the old wheel, putting on a new one and re-setting the screw.
  • Increase the speed if the tool cuts slowly, but proceed cautiously.
  • The electrical box will heat up as you're cutting, so don't touch it or you could be burned. Protective gloves will prevent burning, but they may also interfere with your ability to guide the tool accurately.
  • Wear safety glasses and a respirator mask. Metal cutting produces fine metal particles that can damage your eyes and also damage your lungs if you inhale them.

© Demand Media 2011