Guide To Types of Drill Bits
The variety of drill bits can be a little intimidating. Here's an overview of drill bit types, and the projects for which they work best.
Most DIYers recognize the importance of using the right tool for the job. But while they may spend hours researching what drill to purchase, they often fail to give enough consideration to what will actually be in contact with their work material: the drill bit.
Choosing the right drill bit is about saving your single most important resource — your time. So for peak efficiency, it pays to understand the different types of drill bits, and which one is right for your project.
What Is a Drill Bit?
A drill bit is a rotary cutting tool that makes holes. The point of the bit contacts the material you’re drilling into, while the shank — the back end — is clamped in place by the jaws of a drill chuck.
There are many types and styles of drill bits, enough to fill an entire aisle in a hardware store. For our purposes, we’ll be focus on those most widely used in DIY projects.
What Are Drill Bits Used For?
Drill bits are primarily used for creating circular holes in materials from drywall and wood to metal and masonry. They might create a hole for an anchor or fastener, or a passage to feed wiring. Bits are sold individually and in multi-sized sets, commonly called drill indexes.
When selecting a drill bit, consider its physical shape, what it’s made of, and the work material you’re drilling into.
Drill Bit Types: Physical Shape
The easiest factor to consider when selecting a drill bit is its physical shape.
A twist bit (sometimes called a fluted bit) is far and away the most common type of drill bit, probably because it’s the one with the greatest number of uses.
A twist bit gets its name from the spiraled grooves, called flutes, along its body. As the bit bites into the work material, the flutes direct waste material up and out of the hole. Twist bits are generally the starting point when drilling a hole. Many drill bits, such as brad bits or masonry bits, are variations on the basic twist bit structure.
But there’s a limit on the size of twist bits, beyond which the weight and heat become impractical. In general, twist bits work well for holes up to one inch in diameter. Holes larger than an inch require a spade bit or hole saw.
A spade bit is flat, with a sharp point in its center and material flaring out to either side, like a pair of bat wings. Spade bits remove a large section of material.
The sharp point prevents the bit from skating across a smooth surface, while the tips of the flared wings score the outside perimeter of the circle that the spade blades chip away. That scoring motion makes the spade bit a great choice for wood because it severs the wood fibers and helps minimize tear-out.
A hole saw also removes a large amount of material. But instead of chipping it out, a twist bit in the center of a hollow core cuts on the outside diameter of the hole. That leaves a round disk or core of material.
Step bits function as multiple drill bits in a single tool. Instead of a cylinder, these are cone-shaped, with a distinctive stair-step profile. Each “step” is one drill size larger than the next. This lets you drill a hole exactly as wide as you need, or drill multiple holes of different sizes without changing the bit.
Drill Bit Types: Drill Bit Material
Drill bits can be made of various materials. The following are far more likely to be useful to the average DIYer (and in their price range.)
These are robust steel drill bits, good for drilling into wood, plastic or metal. One downside: At high drill speeds, they can overheat and soften, becoming dull. This is especially common when drilling metal.
High-speed steel (HSS) bits are capable of prolonged drilling without losing their edge. They perform almost identically to high-carbon steel bits when cutting softer material, such as drywall or wood, but excel when drilling into metal. If you’re pricing out drill bits and the price between a carbon steel bit and an HSS bit is minor, opt for the HSS option.
Carbide or carbide-tipped
Drill bits made with carbide or carbide-coated tips are significantly more durable than steel bits, but also cost significantly more.
Most DIYers don’t need the extra resiliency of a carbide-tipped drill bit. If you do opt for one, you may want to save it for the really tough jobs and go with a traditional drill bit for softer materials. Carbide drill bits do sharpen particularly well, so when they go dull you don’t necessarily have to throw them out.
Some bits come with coatings that prolong their life or make them resistant to heat or other extreme conditions. These include titanium and even crushed diamond.
Drill Bit Types: Working Material
Here’s how to select the best bit for the application at hand.
Drill bits for metal
For drilling into metals such as stainless steel, your best bet is a HSS twist bit. High-speed steel offers greater resistance to the high temperatures generated when drilling into metal, and the flutes on a twist bit will throw off metal strands that are relatively easy to clean up.
If you’re working with thin material or widening existing holes, use a step bit to get exactly the size you need. For creating holes of one inch or more in metal surfaces, consider a hole saw.
Drill bits for masonry
Masonry drill bits are good for surfaces like concrete, brick or mortar. They’re normally twist bits with a carbide fin at their point. The fin breaks up the masonry, while the flutes on the body remove the waste material.
Masonry bits are often used with a hammer drill, a specialized tool that adds a rapid hammering action to the bit. That allows it to reach fresh masonry and remove dust more efficiently.
Drill bits for wood
The go-to bit for wood is a twist drill bit. A brad point on a drill bit will create a bit of “bite” and help prevent the bit from walking across the surface as you get up to speed. For holes of one inch or more, consider a spade bit.