They Key To Drilling Perfect Holes: Drill Bits

By on September 1, 2015
drillbit

Installing a lockset, running sheathed electrical wire in wall framing, bolting a gate latch, installing an expansion anchor in concrete, mortising a cabinet door hinge, hanging a plant from the ceiling, installing a towel bar in a tile shower, and running computer cables through a countertop — these are but a few of the many jobs around the house that require a drill bit.

There are almost as many drill bits from which to choose, as there are different uses. Some drill bits are flat, others are short and squatty, and still others are long and narrow. Which bit is right for the job? It depends – on the job, that is.

There are, however, a few common rules that apply to all drill bits regardless of shape, size or application -quality, maintenance and safety.

Quality. First, a drill bit is a tool. Any job worth doing is worth doing well. And doing it well means having the right tool for the job. Keep in mind that tools are an investment that, with proper care and maintenance, should outlast the user. Many tools in our family have been passed down through several generations. Thus, when tool shopping we suggest that you bite the bullet and spend a little extra up front for name brand, better quality tools. You’ll get better results, the tool will last longer, and you will be money ahead.

Maintenance. A drill bit is essentially a cutting tool and, thus, must be kept sharp. A sharp drill bit will require less physical effort, exert less stress on a drill motor, produce better results and make for a safer work environment. Aside from keeping bits clean, they should be stored in a container or “drill index” that will prevent them from rolling around (as in a tool box) and becoming nicked and damaged. Drill bits should periodically be sharpened to keep them in peak working order. Most twist bits can be sharpened using an electric drill bit sharpener. It’s the perfect gift for the do-it-yourselfer who has everything. Other bit styles should be taken to a company that specializes in sharpening blades, bits, chains and other cutting tools.

Safety. Boring and drilling will produce splinters and metal shavings that can result in serious injury. Therefore, always wear safety glasses and consider wearing a pair of snug fitting work gloves. And since most boring and drilling is done with a power driver drill, use extreme caution when operating the device. Drill bit can “walk” along the surface of the material being drilled forever damaging it. Also, bits can bind in the material being drilled and (under extreme conditions) can result in a sprained or broken wrist.

Not all bits are alike. The most common style is the “twist” bit. Although it is designed primarily for use with metal, it has been adopted as a multipurpose bit by most do-it-yourselfers. This likely has something to do with the wide range of sizes available from 1/64 to ¾ inches. The twist bit or “twist drill” has two helical flutes that run about two-thirds along the length of the shaft. These flutes act to clear the waste material from the hole as the drill rotates and is moved in and out of the hole. It is actually the outside edges of the spirals or “margins” that form the true diameter of the bit. The balance of the bit structure is slightly recessed to prevent drag and the resulting friction.

Bits designed for use with metal are made of “high speed steel” (HSS) because they can withstand high temperatures. In contrast, bits made from “carbon steel” will work well for wood, but should not be used for drilling metal since they tend to be more brittle and less flexible than their HSS counterpart.

Other features that influence the quality of a drill bit are the tip and finish. A bit with a multi face carbide tip will act like a hot knife through butter and resist wear. Some twist bits are finished with Titanium nitride (TiN) or Cubic Boron Nitride (CBN), which act as both a lubricant and bit hardener. Their gold cast can easily distinguish TiN and CBN bits.

Although some of the modern “multipurpose” bits are the super heroes of drill bits and, as the name implies, can perform well with many materials — drilling into concrete, brick, block or stone can take the average twist bit to task. Thus, when drilling into one of these tough substances, we suggest that you kick it up a notch and opt for more drilling horsepower by using a masonry bit. The cutting tip is made from tungsten carbide bonded to a spiraled steel shaft. Use a masonry bit when installing an expansion anchor into concrete.

A masonry bit can be used to drill tile provided that it is used at slow speed and without the hammer action that is often used when drilling concrete or stone. Better yet, consider using a tile bit that has ground tungsten carbide tip. Best used with a variable speed drill at slow speed, a tile bit should always be used with a lubricant such as turpentine to keep the tip cool. Use a tile bit when installing bath accessories (such as a towel bar) into tile.

Though twist bits are the most recognizable style of drill, flat wood bits or “spade” bits run a close second. Although the spade bit can be used with a variety of materials it is used primarily with wood where large holes are needed. However, the spade bit does more scraping than cutting. A good spade bit will have a sharp point and relieved edges that create a cleaner, cooler cut. As is the case with most drill bits, spade bits are available in various lengths up to 16 inches for added reach.

When it comes to a drilling a big hole with a flat bottom (such as that needed for many styles of European cabinet hinges), a Forstner bit makes easy work of it. The Forstner bit consists of a central brad point for alignment and larger peripheral cutting teeth and is available in a wide range of sizes.

If you are adding on or remodeling and will be running electrical wire through the studs, you should have a “wood auger” and a half-inch drill motor handy. The wood auger isn’t designed for “pretty work” – it’s purpose is to get the job done! And that it does. The wood auger has a lead screw tip that pulls the bit through the wood for quick, large diameter holes that most residential pipe and wire can easily fit through. So powerful is this bit that six standard two by fours sandwiched together don’t phase it.

If you’re tired of computer cables all over your desk and can benefit from a little “cable organization,” then a hole saw is just the answer. A hole saw consists of a steel cup with a saw-teeth rim. They are available in units of fixed diameter and can be purchased individually or as a set with an interchangeable mandrel that houses a replaceable pilot bit. Hole saws are particularly useful for cutting large diameter holes up to 1-½ inches thick. Boring from alternating sides using the same pilot hole can cut thicker material. Since the metal for holes saws is usually tempered, it can be used on metal as well as wood.

Drill tip: always hold the drill square to the work and apply only light pressure when drilling.

 

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