The Hole Truth About Drill Bits

What do ancient Egyptians have in common with today’s alarm installers? Both make a living by using a drill. Even though there is evidence that the Egyptians used drills as early as 4000 B.C., present use of the drill bit dates back to 1863 and inventor Stephen A. Morse.

Today, more than 700,000 drill bits are used daily. A professional installer realizes that his or her work is only as good as the tools he or she uses and maintains. The misunderstood drill bit is one of those tools that is used and often abused.

Let us take a moment to look at the different types of drill bits, their uses, and ways to keep this valuable equipment sharp and performing optimally. Along with this, we will gather some tips and insight to make our installations easier and more productive.

Dissecting a Drill Bit

The first step is to learn about some of the general anatomy of a twist drill bit:
  Chisel Point—The central tip of the drill where the removal process starts
Cutting Lips—Leading cutting edge of the drill point that begins to scoop up the material and make chips
  Heel—Trailing edge of the drill point
Flute—The spiral grooves that remove drill debris out of a hole
Lands—The flat spiral area separating the flutes
Margin—The sharp edge of the land, which assists in reaming out the hole
Shank—The end of the drill bit that connects to the drill chuck. A shank surface can be smooth, as with high-speed steel (HSS) bits or with impact-type drills, or keyed in a ribbed spline or slotted drive shank (SDS) configuration to reduce slippage in the drill’s chuck.

Drilling Down Further

Next, familiarize yourself with the specific types of drill bits, which are:
Twist Drill Bit—Sometimes referred to as a high-speed steel (HSS) drill, it is the most common drilling tool, and is typically sized at less than 3/8 inch. Some installers may be familiar with the long version of this bit, which is known as a bell hanger.
  Augur Bit—The screw center bites and pulls quickly into wood, while the large cutter and flutes do a very good job of removing chips.
Forstner Bit—This bit has a very sharp cutting rim. Since there is not a central starting point, the bit walks easily, making freehand drilling difficult.
Mutispur Bit—Has a spur configuration reminiscent of the round chisel blade on the Forstner, but has a starting center point to reduce walking.
  Spade Bit—An economical, flat paddle-shaped wood bit for large, coarse wood holes. It has a starter point for easy centering, requires a powerful drill and can be easily field sharpened.
Step Bit—This has the appearance of a child’s top with ridges. It allows an installer to size a hole in a metal box or other thin material such as plastic and wood.
Hole Saw—This is technically a saw that acts like a bit. It has a centering pilot bit and comes in bimetal versions.
Saw Drill—A special drill used as a high-speed router-type saw. The cutting action is achieved by pressing the saw drill against the material and using the flute and land action. This allows for very smooth and fast cutting of irregular openings in material such as wallboard.
Masonry Bit—This is a hardened steel drill bit with bonded tungsten carbide cutting tips. It is specifically designed for drilling in concrete, brick, block and stone.
TiN-Coated Bit—This type of bit has its surfaces treated with a titanium-nitride compound, which improves drill life by reducing wear and increasing heat resistance.

Putting the Bits Together

Following is some basic advice for working with drills and drill bits:
  • The larger the drill bit size, the slower the speed.
• Stop using a dull drill bit when feed-through appears to go down.
• Never use a bent drill bit.
• Oven cleaner can be used to remove residue buildup on wood drill bits.
• Don’t drill a hole past the flute length.
• Drill a pilot hole first for large holes in metal.
• When using masonry bits in concrete, make sure to stop as soon as you hit metal as the heat will destroy the bit. Then use a rebar (steel rod) cutter bit to cut through the metal rebar. Use metal detectors to detect metal in masonry. Avoid drilling blind in masonry.
• Minimize heat buildup by making sure hammer drill shanks are lubricated per the manufacturer’s instructions. Hot bit shafts may break.

Be a Sharp Sharpener

A good sharpening program can save a dealer money in replacement drill bits. Learning to sharpen drill bits can be accomplished at different skill levels.

Care should be taken when sharpening long flexible-shaft bits in a machine. You have two choices; either use the long shaft adapters where the bit can be temporarily removed or have another person assist in holding the long shaft bit as it is being sharpened in order to maintain the correct drilling angle. Freehand filing sharpening techniques on bits such as the auger, spade and multispur can be learned with a little practice.          Bob Dolph is based in Orlando, Fla., and has served in various technical management and advisory positions in the security industry for 25 years. He is currently a training and products consultant. To share tips or ask questions about installation or troubleshooting, E-mail Dolph at

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