A spiral saw, which is actually a mini router, is one of the best tools for cutting openings in drywall for electrical boxes. It lets you cut holes quickly and accurately without the time-consuming measuring and marking usually required. And once you get the hang of this tool, every box will be perfectly cut out, reducing the amount of time you'll spend patching.
With special bits, spiral saws can also cut wood and some types of soft tile. With the mini angle grinder attachment, you can mount a diamond blade, metal cutting discs and sanding discs to your saw. Other attachments, like a flexible shaft for getting into tight spots, are also available.
This specialized tool is especially worth buying if you have a big drywalling job on the horizon. In this article, we'll show you how to cut around electrical outlets and lights when you're hanging drywall. We'll also show you a few other handy uses for a spiral saw.
You'll find spiral saws in the tool section of home centers, at drywall suppliers and at online tool sellers. For maximum versatility, consider buying the kit that contains the angle grinder attachment. You'll also need bits. For drywall work, buy a package of guidepoint bits. Spiral saws are noisy and dusty, so don't forget your safety gear. Safety glasses, hearing protection and a good-quality (two-strap) dust mask are essential.
After you insert the bit into the collet, pull it out until about 1/8 in. of the smooth part of the shank is showing before tightening the collet. This will help prevent bit breakage. Then adjust the base so that the bit protrudes about 1/4 in. beyond the depth of the material you're cutting.
When you use a spiral saw to cut outlets, there's no need for precise measuring. Simply mark the approximate center of each electrical box or other opening on the face of the drywall and cut them out after the sheet is loosely attached to the framing. Before you hang the drywall, turn off the power to the electrical boxes. Then press the wires to the back of the box to avoid damaging them with the bit. A hammer handle works well for this job.
When you hang the sheets, don't place any fasteners within about 16 in. of an electrical box until you've cut it out. Otherwise, the drywall is pressed against the box, and it will break out before you finish the cut, creating extra patching work. Use symbols to mark nonstandard boxes so you'll have a better idea what you're cutting around. For example, draw a square for doublewide boxes or a circle for round light fixture boxes. Make sure you mark and cut every box. Searching for missing electrical boxes buried in finished walls is no fun.
Cut counterclockwise when you're going around the outside of a box, window or other protruding object (Photo 3 below).Move the spiral saw clockwise if you're cutting around the inside of an opening such as a hole in the wall for a recessed medicine cabinet.
Cutting around a plastic electrical box isn't quite as easy as it looks. I recall that on my first attempt I put too much pressure on the bit and cut right through the side of the soft plastic box. Try to apply just enough pressure to keep the tool moving around the outside edge of the box. Concentrate on feeling the edge of the box. Before you tackle the real thing, mock up a practice board by nailing a spare plastic box to a stud and covering it with a scrap of drywall. Practice routing around the box until you get the hang of it.
This circle-cutting attachment is great for jobs that require a precise circle, such as cutting round holes for remodeling-type recessed lights, which require you to insert the light/box combination after cutting the hole. Make sure you know where the ceiling joists are so you don't cut over them.
Don't throw away your jigsaw—cutting wood with a spiral saw is slow and noisy. But for tight spots and intricate cuts, a spiral saw is a handy tool to have. For wood cutting, install a spiral-cut wood bit. Since these bits aren't designed to drill straight down into the wood, use the method shown in Photo 1 to start the cut. Once the bit is through the wood and the base of the spiral saw is flat on the surface, you can cut out any shape freehand. Follow the recommendation in Photo 2 for turning corners. Keep in mind that 3/4 in. is about the maximum thickness you can cut, and even that is slow going.