How to Properly Use a Hole Saw

Hole saw basics

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Photo 1: First bore a pilot hole

Mark the center of the hole and drill a 1/8-in. pilot hole completely through the door to transfer the center to the other side. Keep bit level and square to door.

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Photo 2: Align bit for full contact

Align the center bit with the pilot hole. Grab the drill firmly with both hands and press straight in. Run the drill slowly and adjust the angle until the hole saw teeth are contacting the wood evenly.

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Photo 3: Start slow and increase the speed

Increase the drill speed and push in with moderate pressure after the teeth of the hole saw have cut a 1/8-in.-deep groove. Run your drill at almost top speed for drilling in wood and slow speed for metal. Slow the drill speed and back out the hole saw occasionally to clear the sawdust out of the groove and keep the hole saw cool. Drill about halfway through.

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Photo 4: Finish the hole from the other side

Align the center bit with the pilot hole on the opposite side of the door and complete the hole. Brace the drill against your hip for extra power and better control. The wood plug will stick in the saw and pop out the other side.

Spade bits are the tool of choice for drilling holes up to about 1-1/4 in. in diameter for running electrical wiring and other uses. But when it comes to drilling really big holes for locksets or plumbing pipes, reach for a hole saw. A hole saw is a steel cylinder with saw teeth cut into the top edge. Hole saws don't cut as quickly as large boring bits driven by a pro's powerful 1/2-in. drill. But boring bits are expensive ($30 plus drill rental). Hole saws, on the other hand, are readily available at hardware stores and home centers for as little as $5 and work with a standard 3/8-in. drill. Cutting clean holes with hole saws requires a little skill and practice. Here are the key techniques that will make the task safer and give you the best results.

Proper setup is important
Mount the correct-size hole saw in the arbor. If your hole saw has an adjustable center bit, make sure it protrudes past the toothed edge of the saw about 3/8 in. (Photo 2). If the center bit has a flat spot on its shank, align this with the setscrew. Then tighten the setscrew to secure the bit. Finally, tighten the hole saw in the chuck of a corded 3/8-in. variable speed drill. Cordless drills won't have enough power unless they're 18 volts or larger.

Start slowly and hold on tight
Photos 1 - 4 show how to drill a hole in a wood door for a lock or door handle, but the same techniques apply for drilling other holes. When you need a clean, splinter-free hole, drill in from both sides (Photos 1 and 4). The key to getting a perfectly straight hole is to ensure even contact at the start. That will put your drill at a right angle to the door (Photo 3).

A hole saw is a steel cylinder with saw teeth cut into
the top edge.

Buying Hole Saws

For as little as $15, you can buy a set of carbon-steel hole saws for drilling wood. For about $45, you can buy a set of bimetal hole saws that will cut wood and metal and last a lot longer. You can also buy specialty hole saws coated with Carborundum or diamond grit to cut hard materials like tile and stone. These saws, however, won't cut wood. Most hole saws mount to a separate centering guide called an arbor. Others are one piece. Better arbors (about $12) have two pins that slide into holes in the bottom of the hole saw to lock the saw in place. Match the arbor to your saw and check that it will fit in your drill. Some arbors require a 1/2-in. chuck and drill.

Enlarge existing holes

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Photo 5: Clamp a scrap piece over the hole

To enlarge an existing hole, first clamp a scrap of 1/4-in. plywood over it to provide a solid surface for the center bit.

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Photo 6: Mark a new center on the scrap

Mark the center of the new hole on the plywood and drill a pilot hole through the plywood. Align the center bit of the hole saw with the pilot hole and bore the hole.

There's just one problem when you need to enlarge an existing hole. The center bit on your hole saw must be engaged in wood before you can start a hole; otherwise, the saw will just spin and gnaw its way across the surface, leaving a mess behind. Clamping a 1/4-in. piece of plywood over the existing hole is the easiest solution (Photos 5 and 6). Another method is to jam a wood plug into the existing hole.

Chisel out the core for deep holes

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Photo 7: Use a side handle for deep or large holes

Drill until the hole saw reaches its full depth. Remember to withdraw the hole saw every five seconds or so to clear the sawdust from the groove. If your drill has a side handle like the one shown, use it to provide a firmer grip and better control.

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Photo 8: Remove the wood so the saw can go deeper

Chisel out as much of the wood plug as possible

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Photo 9: Finish the hole

Repeat the drilling and chiseling process until you're all the way through.

You can drill deep holes with a hole saw if you chisel out the wood plug as you go (Photo 8). This is useful when you only have access to one side of thick material and your hole saw isn't long enough to go all the way through. If you don't have a chisel handy, break out the plug with a standard screwdriver.