Everything You Didn't Know You Needed to About Drill Bits

A close-up of a drill and sawdust.

A drill bit might look like a simple tool, but a lot of engineering and design goes into its production. In fact, each bit is designed with a specific purpose in mind, whether it’s drilling a one-inch hole through wood or step drilling through sheet metal. With that in mind, here is everything you should know about drill bits.

Shank Size

The shank is the part of the bit that fits into the drill chuck, and it can come in a variety of different sizes. The size and shape of the shank actually has significant impacts on the drilling process. Most shanks are reduced in size to fit a 3/8” chuck and commonly come in the straight variety. Hexagon shaped shanks, however, are better for boring through harder materials and have less slippage.

Tip Angle

A collection of drill bits.

The angle of the tip of the bit, or the point angle, depends on the type of material the bit is designed to cut. A wider angle is used on hard materials, like metal, while a shaper angle is used on soft materials, such as wood. The angle of the tip also affects the shape of the hole, the rate of wear on the bit, and chatter.

Lip Angle

The lips of a bit are the parts that do all the cutting, and the angle of the lips determines the aggressiveness of the cut. If the angle is too great or small, the bit might bind up during cutting and even break. A proper lip angle, which is determined by the point angle, will ensure a clean cut with less point pressure.

Bit Length

A collection of drill bits.

It might not be immediately obvious, but the length of the flute will determine the maximum depth of cut. The length of the bit, minus the shank, also affects the accuracy of the hole and stiffness of the bit. Long bits can bore deep holes, but they are also more flexible and can result in inaccurate or wandering cuts.

Twist Bits

The most easily recognizable and commonly found drill bits are called twists. These bits have a pointy end and a spiral groove that helps to eject material. One reason they are so popular is because they work on a wide range of materials, from soft woods to certain metals. When drilling through harder materials, these types of bits are often coated to make them more durable. The downside to the hardening process is that the bits also become more brittle and can break if not properly used.

Spade Bits

Spade drill bits.

If you need to drill a quick hole through wood and are not concerned about splintering, then a spade bit is the one for the job. Not only are these bits very budget-friendly, but they come in a variety of diameters and lengths to fit just about every need. The only downsides are they often cause splintering in wood and require a lot of torque. If you want a neater hole in wood, then consider using an auger or Forstner bit.

Step Drill

Although expensive, step drills can cut a variety of diameters and are great for thin materials like sheet metal. These drill bits have a stepped profile and increase in size the deeper the hole. The downside to step bits is that they do not work on materials thicker than 3/16 of an inch. Also, they might require a pilot hole before drilling.

Masonry Bit

A construction worker with a masonry drill bit.

Aptly named, these bits are made for boring into brick, stone, quarry tiles, concrete, or blocks. Their tips are made out of tungsten carbide for maximum hardness. Masonry bits can be used in a power drill or hand brace, though the latter might shatter the bit. Unlike some coated bits, these types can be sharpened using a grindstone or drill sharpener.

Operating Tips

Use slow speeds for drilling hard materials and fast speeds for soft materials. As you near the end of the hole, slow down to ensure accuracy. With metals, it's a good idea to use a cutting fluid for better results. Whenever drilling through wood, clamp a backing board to the material to lessen the chances of blow-out. Never cool a drill bit with water or any other fluid. Instead, allow the bit to cool naturally.

Over time, a drill can become dull and not cut as cleanly as you need for a project. An easy-to-use sharpener, like Drill Doctor, can help you keep your drill bits in perfect condition so your work goes faster. Sharpening drill bits instead of replacing them can save money over time, especially as your collection builds.