What is Drill Bits And Their Types?

As a DIYer, you will need the right tools to achieve a high-grade finish when working on drilling projects. So, as you spend hours researching what drill to buy for the projects, remember to consider the types of drill bits to go for.

Drill bits are designed for specific projects, materials, and precision levels. Therefore, the best way to achieve maximum working effectiveness on your drilling projects is to understand the different types of drill bits and where exactly each one is suitable.

What Are Drill Bits?

drill bits

Drill bits are cutting tools usually attached to a drill to make holes through different materials, primarily circular cross-sections. They have a spiral groove (commonly referred to as flutes) that helps remove debris as the drill bit rotates, allowing for efficient drilling.

There are many different types of drill bits, which are either sold individually or in multi-sized sets (drill indexes). Now, let’s check out the most popular types of drill bits used in DIY projects. But first, what are drill bits used for?

What Are Drill Bits Used For?

Drill bits typically drill holes in wood, plastic, drywall, masonry, and metal. They create circular holes for anchors and fasteners or to pass through wirings. To make holes, drill bits are mounted to a drill; the point of the bit contacts the workpiece you are drilling into, while the drill chuck secures the shank of the bit.

The effectiveness of a bit can be influenced by its physical shape, the material it’s made from, or the material you’re drilling into.

Types of Drill Bits

types of drill bits

You will need to use the right types of drill bits to drill holes with precision levels. Here are the popular drill bit types for your next drilling project, whether you’re drilling large or generally small holes.

#1. Twist Drill Bits

Twist drill bits

Twist drill bits, also called twist drills, are DIYer’s most popular drilling tools. The front edge blades cut the material and spiral along the hole, remove the scrap from the hole, and keep the cutting straight.

They are used on metal, wood, plastics, or similar materials. Most twist drills are made from either:

  • High-Speed Steel (HSS) – it’s the best option for a wider variety of materials. When boring holes in metals, the HSS can withstand high temperatures.

  • Carbon Steel – these bits are specifically made for drilling woods. Unlike HSS bits, they are more brittle and not flexible enough.

A twist drill bit can also be coated with Titanium Nitride (TiN). This coating helps increase the cutting edge’s hardness with self-lubricating properties. The coating is only effective during drilling, though. The same can’t be said with other materials.

Twist drills size range from 0.8 mm (1/32 in) to 12 mm (15/32 in ) plus. The bits are designed to drill holes so small that they occasionally clog. This is more often when the wood is ‘green.’ So when drilling deep holes, especially in hardwood, the bits must be continually removed to remove the debris.

#2. Masonry Drill Bits

Masonry Drill Bits

Masonry drill bits are effective on brick, mortar, and concrete. They resemble large twist drills with a corkscrew shape, but a little tighter, and a carbide fin at their point. The fin does the masonry, while the flutes on the body clean the waste. Thanks to their wide arrow-shaped heads, it’s easy to distinguish them from the twist drills.

Masonry bits are usually used with a hammer drill bit that provides an extra hammering effect to the bit. This results in optimized performance because the hammer drills can access fresh masonry and get rid of dust more easily. Although these bits can be used on wood, the holes will be ragged and take longer than the wood drill.

These drill bits’ size range from 4 mm (5/32 in) to 16 mm (5/8 in). You can also find long masonry drill bits ranging from 300 mm (11 13/16 in) to 400mm (15 3/4 in) for drilling masonry walls.

#3. Cobalt Drill Bits

Cobalt Drill Bits

Cobalt drill bits combine high-speed steel and cobalt for added strength and heat resistance. Such drill bit types are employed for drilling hard metals like cast iron, cast steel, stainless steel, bronze, and weld seams.

Like the other high-speed steel drill bit types, the cobalt drill bit is corrosion-resistant; it’s unlikely to change in all exposures, both in storage and use. On the contrary, cobalt can be very brittle. When these drill bits are not maintained properly or dropped, they can break, becoming costly.

The typical sizes range from 1.6mm (1/16 in) to 6.4 mm (1/4 in).

#4. Brad Point Drill Bits

Brad Point Drill Bits

The Brad point drill bit is equipped with Brad point tips (also called W-point tips), which allow the outer cut edges to cut the hole diameter before the center punches through the material. It induces the chisel not to grab and hit the same spot, delivering an ultra-clean hole. 

This makes it ideal for deep penetration into wood, plastics, and tasks like dowelling. These drill bit types are often sold with rubber rings called depth stops, which fit around the drill bit to allow you to determine precisely how deep of a drill hole you want to create.

Brad point drill bits’ sizes range from 3.2 mm (1/8 in) to 12.7mm (1/2 in).

#5. Forstner Drill Bits

Forstner Drill Bits

These drill bits are one of the most specialized drill bits used to install concealed hinges [diameter usually either 26 mm (1 1/32 in) or 35 mm (1 3/8 in]. These drill bits drill large holes in wood; their flat bottoms allow you to pull it slightly from the wood piece. 

There are two shapes of Forstner bits: one with a continuous rim and another with a saw-tooth rim. Continuous rim bits leave a very clean edge and are most suited to small holes, while the saw-tooth pattern bits produce relatively rough holes, but they are great for big holes [over 25mm (31/32 in) in diameter] and are more durable.

Forstner drill bits can be attached in a handheld drill, but the forward pressure needed to run them is higher compared to other typical drills. That said, a drill press machine would be more appropriate.

#6. Countersink Drill Bits

Countersink Drill Bits

When viewed from the side, a countersink bit looks similar to an arrow tip. It has a cone-shaped tip with flutes. Some countersink bits lack flutes (except for the center drill) and, as a result, shave away the material easily. Others are designed similarly to the twist drill with a replaceable center drill. 

You can use a countersink drill bit if you’re just boring holes fit for flat-head screws. They create cone-shaped holes, which serve as a recess for the screw to fit into it without jutting out. This will make the outcome look attractive and create a strong attachment.

Countersink drill bits usually come in 13mm (33/64 in), 16mm (5/8 in), and 19mm (3/4 in) sizes.

#7. Plug Cutter Drill Bits

Plug Cutter Drill Bits

Plug-cutter bits are commonly used in professional woodworking and furniture creation. For projects that you intend to hide bolts, screws, and other recessed fasteners or soon-to-be varnished projects, you can use this drill bit to cut the wooden plugs.

The drill bit usually comes with four sharpened cutting blades to drill through the wood and a hollow center to secure the wood plug.

You will need a drill press as the drill bits don’t have a center point to keep them aligned and steady. Besides, with the drill press, you will have control over the precision level of the cut.

The most common sizes are 9.5 mm (3/8 in), 12.7 mm (1/2 in), and 5.9 mm (5/8 in).

#8. Auger Drill Bits

Auger Drill Bits
Auger drill bits are wood boring bits ideal for drilling long, deep holes into thick woods. The drill bits come with a screw tip that draws it into the workpiece, getting rid of the need to push. Besides, the single-spur cutting edge of the bit seamlessly marks the hole’s circumference, ensuring a polished finish, while its large flutes efficiently remove chips and dust.

Auger drill bits have hexagonal shanks, creating a more secure and firmer connection between the drill bit and the chuck. Moreover, some auger bits have a hollow center, which offers more chip removal, allowing for deeper drilling, while others come with a solid center, making them more rigid and robust.

An auger drill bit can reach about 18 inches in length. For the diameter, the size ranges between 6 mm (15/64 in) to 25mm (31/32 in).

#9. Spade Drill Bits

Spade Drill Bits

A spade drill, also referred to as a paddle bit, is commonly used by DIYers with outstanding woodworking experience. Besides, the drill bit is used by electricians to drill holes for running cables.

Most spade drill bits have a sharp center point and flattened blade for increased accuracy. The sharp center point usually prevents the drill bit from sliding across a smooth surface, while the flared wing tips score the outside perimeter of the circle chipped away by the flattened blade. Some spade drill bits have points at the two edges, helping create an exit point and a neater hole.

Spade bits are specifically used for drilling large holes up to 1-1/2 inches in diameter through wood. They have a diameter size range of 6 mm (15/64 in) to 38 mm (1 31/64 in) and can be connected to an extension shank to increase their reach.

#10. Installer Drill Bits

Installer Drill Bit

As the name suggests, installer drill bits are used for installation purposes, such as installing wiring. It is a specialized twist bit primarily used by electricians, cable installation experts, and security system technicians. This drill bit can be up to 18 inches long, making penetrating through floors, walls, or other surfaces easier.

You can conveniently use the installer drill bits to drill through plaster, mortar, and wood. Being an installer bit, it comes with a small hole in the tip where you can secure a wire once you have drilled through the workpiece. After drilling and securing the wire, you can pull the wire using the drill bit through the drilled hole. You can then connect the wire to another wire, making your installation project much more straightforward.

The diameter ranges between 9.5mm (3/8 in) to 25.4mm (1 in).

Drill Bit Angles Explained

Drill bit angle comes from the time when DIYers relied on manual drilling, and the drill bits had conical shapes. It is the angle between the cutting lip and the spur on its point.

Usually, there are two main drill bit point angles: 118° and 135°. The key difference between the two point angles is the shape. A 118° bit is more pointed and steeper and comes with a smaller chisel.

Moreover, the 118° bit drills more aggressively and is primarily used for drilling holes into soft materials such as wood and plastic. Although you can also use it to drill steel materials, the steeper cutting angle will cause it to dull rapidly.

On the other hand, a 135° bit is usually used for drilling holes into harder materials such as stainless steel, as the pitch makes it much easier to drill repeated holes into these materials. Since a 135-degree bit is flatter than a 118-degree, more of its cutting lips usually engage with the workpiece surface sooner to start the full metal drilling process.

For most types of drill bits, the angle of the point is vital in determining the type of material the bit can drill.

How to Choose the Right Drill Bit for Your Project?

#1). Consider the Material You Intend to Drill

Consider the material you will work on when choosing a drill bit for your drilling projects. Different materials usually require different drill bit types for the best results. For instance, soft materials such as plastic and wood can be drilled using an HSS drill bit, while hard materials such as concrete and metal require specialized drill bits like carbide or cobalt.

#2). Consider the Material of the Drill Bit

The drill bit material is also crucial in choosing the right bit for your project. Every material is unique. For instance, cobalt drill bits are quite hard and distribute heat faster, while high-speed steel (HSS) bits can conveniently drill through wood, PVC, fiberglass, and aluminum.

#3). Consider the Size of the Drill Bits and the Size of the Hole

Drill bit sizes are measured in millimeters or inches. When choosing the right drill bit, pay attention to the size of the drill size and the size of the hole you want to drill. Using drill bits that are too big or too small can result in an undesirable hole.

#4). Consider the Bit Coatings

The coating on a drill bit is crucial because it enhances its durability and heat resistance. For instance, when HSS bits are coated with titanium nitride, they get very hard, enhancing their suitability for drilling holes in hard materials.

#5). Consider the Shape of the Drill Bit

The shape of the drill bit is also crucial in choosing the right drill bit for your project. For instance, spade drill bits are suitable for drilling large-diameter holes in wood, while Forstner drill bits make clean, flat-bottomed holes in soft materials like wood. Twist drill bits, on the other hand, are versatile and ideal for various materials.

Tips for Proper Drill and Drill Bit Maintenance

#1). Clean the Drill Bits Regularly

Ensure you clean your drill and bits regularly. To do so, detach the drill bit from the drill by following the manufacturer’s instructions. Then, wipe off the dust, debris, and swarf with a dry clean towel. You can use a toothpick or brush to remove the debris from the bit’s cutting edges and flutes.

Keep in mind that regular cleaning of your drill and drill bits is crucial for optimal performance.

#2). Keep your Drill and Drill Bits Away From Water

Store your drill and drill bits away from water. If you have a corded or cordless electric drill, storing it in a dump place can cause permanent damage. Besides, water can cause the drill and drill bits to rust. We encourage storing these drilling tools in a dry place to protect them from water damage.

#3). Lubricate your Drill Regularly

To maintain the effectiveness of your drill, we recommend lubricating it regularly. Refer to the user’s manual for more insights on lubricating the drill.

You can use oil to lubricate the drill’s chuck to rotate more smoothly.

#4). Wait for the Drill and Drill Bits to Cool Before Storing them

Power drills normally generate heat due to friction as the drill bit spins. So, waiting for the drill to cool before storing it is advisable.

#5) Replace the Dull Drill Bits

Drill bits can become dull over frequent use, losing their sharp point and making using them harder. We recommend replacing them after a period of use to enhance the performance of the power drill and reduce unnecessary wear and tear.


Gavin Leo is a technical writer at Aria with 8 years of experience in Engineering, He proficient in machining characteristics and surface finish process of various materials. and participated in the development of more than 100complex injection molding and CNC machining projects. He is passionate about sharing his knowledge and experience.