Once you’ve learned the basic skills of using a power drill, it’s important to thoroughly understand all of the various bits and accessories that make your drill such a versatile tool. The term “drill bit” is limited to bits that fit into your power drill and drill holes. These are different from “driver bits” which fit into your drill and work as the power tool version of a screwdriver. It’s an easy mistake to refer to both groups as drill bits, but knowing the difference will not only help bring clarity to you and the people you’re talking to, but it will also make you look like you know what you’re talking about. The key to remembering the terms is to attach the appropriate verbs: a driver bit drives screws, while a drill bit drills holes.
The most standard, go-to drill bit for drilling wood, plastic, and even metal, is a twist drill bit. Just like the threads of a screw help it grip into the wood, the grooves of a twist drill bit allow it to glide through your material more easily and create a way for the shavings to escape as you drill.
Different types of drill bits
General twist bits are good for drilling in metal, wood, and plastic. Drill bits with the words “masonry,” “hammer,” “rotary hammer,” or “Impact Tapcon” in their names are all made for drilling in concrete. For DIY purposes, you can generally bypass these. They may work in wood, but they'll cost you more money.
Here's what you need to know when you're scanning the wall of wood drill bits at Dunn Lumber. The Irwin Cobalt is your go-to basic twist drill bit. Irwin’s Turbomax High-Speed Steel Drill Bit is a bit that stays sharp longer and is designed for clean entry and faster drilling. Irwin’s Black Oxide drill bit resists rust/corrosion and reduces friction to speed up the drilling process (but remember—faster drilling doesn’t mean clean holes, and for DIY I generally find that a clean entry is more important).
Another type of drill bit is called an impact drill bit. These bits (as their name hints) are specially designed to be used with impact drivers. An impact driver is made for driving screws into hard surfaces or driving very long screws. Rather than relying on the strength of your arm when you're using a power drill, an impact driver provides added torque to turn the screw. It's good for large timbers, as well as when you have a lot of screws to drive in, and makes jobs like building a deck so much easier. It’s important to always use impact driver–grade bits with an impact driver—otherwise, you risk the possibility of them shearing off. You can easily spot an impact drill bit because of it's hex base.
And lastly, the twist bit with a little something extra is the countersink drill bit. This is a regular twist bit with an attached countersink at the top that drills a larger tapered hole for the head of the screw. The countersink can be loosened and moved along the length of the drill bit to match the length of the screws you’re pre-drilling for. A countersink drill bit isn’t always necessary, but it can definitely elevate the look of your DIY project. Countersink drill bits are helpful for especially hard woods (like ipe) where the screw head has a difficult time embedding in the wood on its own, or for softer woods like cedar where the head of the screw near the edge of the wood will result in the wood cracking and splitting. The numbered system for countersink bits can be confusing (it doesn't line up with the numbered system of screws), so pay attention to the measurements when picking one out.
When to use twist drill bits
You can pretty much default to using a twist drill bit unless there’s a good reason not to. For example, a twist bit is ideal for pre-drilling for screws, drilling a hole partway through your material, drilling at an angle, making an existing hole bigger, and drilling holes in wood, plastic, and metal.
When not to use twist drill bits
You shouldn’t use a regular twist drill bit when drilling through unique material like concrete, tile, or glass. Twist drill bits only go up to about ½” in diameter, so when you need a hole bigger than that you’ll need to opt for a different kind of drill bit. When you need a clean entry and you just can’t get it from a twist bit, a spade bit could do the trick. And lastly, you shouldn't use a twist drill bit when pre-drilling just isn’t necessary. You’ll need to evaluate that on a case-by-case basis, but in general when you’re not driving screws close to the edge, or you’re building something that doesn’t need a particularly neat finish, you can think about dropping this step and saving yourself the hassle.
Twist bit best practices
Be mindful of angle and pressure
Always be cautious with angle and pressure when using thin drill bits, or really long drill bits since there is more chance of breaking the bit. Thicker, shorter drill bits can handle some torque and pressure, but if you’re using something thin like a 1/16” drill bit, any kind of torque will snap it.
Caring for drill bits
Don’t forget to take care of your drill bits! Knock the sawdust out of the grooves before you put them away, and don’t leave them out in the rain (they’ll rust). Drill bits can heat up and will even smoke when used, but don’t worry—this isn’t a problem. Drill bits create friction, and friction creates heat. Drill bits are engineered to withstand heat—just be careful not to burn yourself on that hot drill bit!
Removing drill bits
Because your power drill has a forward and reverse setting, some beginners think that they need to flip to reverse in order to get the drill bit out of the material. I was guilty of this once, but it turns out that it’s very much unnecessary. Leave the drill in forward mode and simply pull. This may seem insignificant, but it really will save you time and allow you to work more efficiently.
Depth, angle, and through drilling
To drill to a specific depth, measure the length of your drill bit and apply tape to the drill bit as a guide to know when to stop drilling. If drilling at an angle, start drilling perpendicular first until the bit bites and then turn to the desired angle. This keeps the bit from wandering. To prevent tear-out on the backside of your material when drilling through-holes, clamp wood onto a scrap piece before drilling. Apply tape to the surface of your material for a cleaner entry.
To determine the size of the drill bit needed for pre-drilling a particular screw, measure the bit against the shaft of the screw so that you can see the threads of the screw peeking out from behind the bit. You want to create room for the shaft, but not for the threads so they have something to bite into.
When pre-drilling for a through bolt, measure the bit against the bolt so that no threads peek out. You want the bit slightly oversized so that the bolt easily slips into place.
To pre-drill for a dowel, you need a little more preparation. If you specifically need a tight fit or a loose fit, pre-drill a hole in a scrap piece of wood then test the hole against dowels in the store (because dowels do range slightly in width). I always regret it when I skip this step.
Pre-drilling for a nail is also an option—you can do this to prevent splitting, or just make the nailing process easier. Pick a drill bit smaller than the nail you plan on using so you end up with a snug fit for the nail.
Twist bits are a simple tool, but with so many variations in size and style, it can be confusing to pick the right one if you don’t know the differences. We hope this tutorial equips you to pick the best drill bit for your next DIY project! To put your new twist bit skills to the test, check out how to build a garden trellis or how to make a bench.