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Ask the Builder: Pick proper drill bit for materials

Sun., Aug. 3, 2014

DEAR TIM: I’ve watched people use electric drills for years but never held one in my hand. Can you give me pointers on how to use a drill and share any tips about drilling into wood, tile, metal and concrete? – Alie W., Morgan Hill, California

DEAR ALIE: As simple as you might think an electric drill is, a new modern drill can be a fairly complicated tool. I remember my first electric drill. It had an on and off switch and a single speed: fast!

Modern electric drills have forward and reverse and variable speeds. Some have hammer action built in that allows you to drill and chisel through masonry at the same time, and some have clutches that stop or slow the drill when a certain amount of resistance is encountered. In other words, a modern electric drill with all these features is a complex tool.

But don’t let that to discourage you. You don’t have to master all of those features on the first day you practice with one.

If you’re going to buy a new drill, one of the first decisions you need to make is between a cordless or a corded model. If you only plan to use it occasionally and not for hours at a time, a cordless drill is perfect. If you plan to use the tool for hours at a time, I’d get a corded drill that operates on the standard 120 volts provided by the electric outlets in your home.

In addition to the drill, there are countless accessories that allow you to drill through just about any material. There are so many that I’ll just give you the very high-altitude overview.

Wood might be the most common material you drill through. There are regular twisted drill bits that do a splendid job of making holes up to ½-inch in diameter. Some have tiny, sharp centering tips at the top of the bit. These spike tips prevent the drill bit from wandering as you start the drill spinning. A wandering bit is a common problem when you drill just about anything, especially metal, tile or any material that’s very hard.

If you want to drill larger diameter holes in wood, you may want to use a spade bit or even a hole saw. These accessories are designed to drill perfectly round holes in materials. As you might expect, there are all different types of spade bits and hole saws, so look at many and read the claims the manufacturers make about them.

My guess is that at some point you’ll need to drill into or through concrete, brick, stone or thick tile. You’ll need a special bit that has a carbide tip on it. Carbide is very hard; only a few materials – like diamond – are harder.

Bits equipped with this tip grind their way through natural stone, concrete and tile. These bits bore even faster if the drill is a hammer drill. Hammer drills rapidly pulsate up and down as they turn. The tool becomes a miniature jackhammer much like the ones workers use to break apart concrete slabs.

If you’re drilling steel or iron, you’ll want special drill bits made for metal. On the label of the bit, it will clearly say it’s made to drill into metal and list the metal types. These hardened bits, when used with oil at slow drilling speeds, cut through metal very quickly. The key to drilling through metal is to keep the drill bit cool. Oil does this by absorbing lots of the heat created by friction.

Here are a few tips I’ve discovered:

• Use a drill press to create perfect holes in thick material.

• Use increasingly larger and larger bits when drilling a large hole in metal.

• To avoid blowouts when drilling cabinet knob holes, use a sharp bit and use minimal pushing pressure just as the bit breaks through the back of the door or drawer.

• Use a handy jig to create slanted pocket holes to join pieces of wood with screws instead of glue.

• When drilling a deep hole in masonry with a carbide bit, pull up on the drill every five seconds to help get concrete dust and particles out of the hole.

• Always practice on scrap material when drilling through anything for the first time.

• The way to become proficient is practice and more practice.

Tim Carter’s columns are archived at www.Askthe Have a question? Just click the Ask Tim link on any page of the website.


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