Drill Bit Basics – The Need to Knows!

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If you’re like me you probably have a couple dozen incomplete drill kits lying around in your garage or shop. You know, ones where the bits are broken, missing, or so dull that you’d struggle to drill through Jell-O on a hot day. On a side note why do we keep broken drill bits? I know I do and my dad used to for the longest times before either of us would throw them away. Anyway, it’s always the same size drill bits isn’t it? Those small bits are especially prone to mishaps. Because, well, the hole still needs to be drilled. But there are a few tips and guidelines that will help your drill bit selection and purchases become more efficient.

Types of Drill Bits

Omitting spade bits and more exotic bits like forstner, wood-boring “twist” bits come in three types; standard, brad point and tapered. Generally the most common bit is the standard, probably why it’s called the standard. These drill bits are the same diameter from end to end and we’ve all used them. These are great for general drilling in most material types. This is the primary style of drill bit I use when drilling pilot holes. For any of you that have ever used a larger one, they do have a tendency to walk especially on any material that is hard like hardwoods or metal. Sometimes I’ll use a center punch to create a divot or start a hole with a smaller drill bit to create a pilot hole for the larger drill bit. Standard twist bits are versatile and handy for most drilling needs.

Brad point drill bits have a sharp center bit generally flanked on either size by shorter sharp tines. Think of a completely round small scale spade bit. These are great for starting a hole in an exact location and minimizing the walking. From what I’ve seen though brad point bits are only made for wood. I guess practically speaking, the sharp tines would probably break off when trying to drill through metal. Or, they’d get really dull really fast. The ones I have used have had very sharp edges, and make very clean holes as a result.

Tapered drill bits, as the name subtly hints at, taper from wide near the chuck to narrower at the tip. These are often recommended for pilot hole drilling because of the shape of a typical screw, which itself is somewhat tapered. As McFeely’s Screw site says, given the proper size pilot drill bit and depth drilled, a tapered drill bit actually provide more strength to the screws grip than either of the two other bit styles.

Size Matters

Nice Chart From McFeely's showing proper pilot bit size

Speaking of proper size, using the correct size drill bit will save you time and can possibly save your project.  For a good rule of thumb McFeely’s suggests using a bit that is the same size as the screw’s shank when drilling into soft woods. When drilling into hardwoods try going a 64th inch larger. Generally, though when I pilot a hole into soft woods I use a 1/8” drill bit for most of my exterior screws. Obviously, too big of a hole and the screw won’t grab and too small of a hole and you run the risk of breaking a screw or cracking the wood.


Drill stop shown on a brad point bit. Photo via Rockler
Finally, when considering depth, stop drilling before you reach the length of your screw. I shoot for ¼” for short screws and a little larger for long screws. Just like using too large of a drill bit drilling too deep prevents the screw from grabbing as tightly as possible. You can achieve good depth by using markers to mark the drill bit or tape. For a more professional looking setup, use a drill stop like the one shown here from our sponsor Rockler. Drill stops are circular pieces of metal (generally) that slide over the bit. They have a set screw that can be tightened down onto the shank of the drill bit. Once the drill stop is tightened down you can only drill to that preset depth.

Photo of author

About Leroy

LeRoy was born into a long line of contractors/carpenters/missing links which maybe why he fell naturally into tools and fishing with his paws, errr, bare hands. He has since punctured, stabbed or electrocuted every appendage that can be discussed in mixed company. Given his natural fur vest, he has never been cold. In his parallel life he is a mild mannered environmental scientist where he builds, destroys and builds again. Which let’s face it is much cooler than Superman’s parallel life.

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