There are many different types of drill bits, all designed for specific purposes. It is important to know the difference between them to ensure you choose the right tool for the job.
There are 4 main types of drill bits, sorted according to the material that they are designed for use on. The categories are wood, timber, and plastics; stone and masonry; glass and tiles; and metals and other materials.
Wood, timber, and plastics
Many different drill bits can handle working with wood, timber, and plastics. You do not necessarily need a lubricating agent when working with wood, although beeswax is a good option if you feel it is required.
These tend to come in sizes ranging from 0.8 to 12+ mm in diameter.
Stone and masonry
These drill bits also do not require a lubricant when in use. Some harder stones, such as slate, are easier to cut through when a little water is added during drilling.
These drill bits have a brazed-on carbide tip at the front of the drill shaft. The flutes and faces of masonry drill bits are ground down in a specific way. This is what makes these drill bits so suited to drilling through breeze block, concrete, asphalt, masonry, and other abrasive materials.
These come in sizes ranging from 4 to 16 mm in diameter. The length can be increased to around 400 mm if a longer drill bit is required.
Glass and tile
These drill bits are always used with water as a lubricant. This is to prevent small fragments from flying off and causing serious harm to the operator.
Metals and other materials
These drill bits are built to handle tough materials. This means that while not designed to do so, they can perform effectively on a wide range of different materials.
When you are using a metal cutting bit, you should always apply a lubricating agent. This reduces the friction that is generated between the drill and the metal being cut. This, in turn, reduces the heat of the drill bit and makes it easier for the drill to cut through the metal. You should never use WD-40 as a lubricating agent. This will dissipate as the drill heats up and become ineffective.
These are generally coated in TiN or TiCN. These stand for titanium nitride and titanium carbonitride respectively. This coating will erode off through use, but they are added to increase the longevity of the drill bit.
Auger
This is a type of wood drill bit. It is shaped somewhat like a corkscrew and works on Archimedes’ principle. The wood is moved from the tip of the drill bit to the back, drawing the wood out as the drill bit rotates.
The tip of this drill bit is pointed and engraved similarly to a screw. This design allows the tip to dig into the wood and helps to keep the drill bit in the correct position within the wood.
Brad point
This is another wood drill bit. It is also known as a dowel, or lip and spur bit. It is designed similarly to the auger drill bit, but the corkscrew shape is more stretched out and the drill bit is narrower overall.
The tip has 3 separate points, unlike the screw tip on the auger bit. There is one point protruding from the centre of the drill bit, and the other 2 are on the exposed ends of the corkscrew protrusions. This tip is not designed to pull the drill bit into the wood like the auger, but instead to keep the drill bit straight.
Bullet pilot
These are similar in appearance to the brad point drill bits. They differ in that they are suitable for use in wood, plastics, and metals. The twisted flutes have been ground down to make a drill bit that is incredibly accurate. They come in sizes ranging from 1.5 to 13 mm in diameter.
Center drill
This drill bit has a tip at each end. It is used primarily for countersinking and tends to be made from high-speed steel. It is most commonly used on wood, plastic, and steel. Provided the drill bit is made from high-speed steel, it will be capable of cutting through most materials.
Cobalt drill
This drill bit is primarily used on metals, particularly harder ones. The primary function of this drill bit is to cut through high-speed cobalt. The shape is similar to that of a traditional drill bit, having a narrow spiral pattern along the length.
Conical drill
Also known as step drills, this drill bit is primarily used on sheet metal. It is a conical shape, tapering to a point at the tip. The primary function of this drill bit is to increase the diameter of existing holes.
Counterbore
This drill bit is designed to create fittings for socket cap screws. Using this drill bit creates a hole that allows the screws to lie flush with the surface of the material they are installed in.
Countersink
There are many different types of countersink drill bits. They are used to create conical holes in a material into which countersunk screws can slot. They are more commonly used on softer materials such as wood, although you can get versions designed to be used on metal too.
Some common examples of wood countersink drill bits are rose head countersinks and a drill countersink combination. For metal, common examples are three-flute high-speed steel and deburring countersinks.
Diamond
This drill bit has small diamond particles to be used as the cutting surface. They are very expensive and tend to be used mostly as an abrasive on tile and glass.
Flat bit
This is also sometimes referred to as a flat wood or spade drill bit. It is primarily used for cutting wood and can come in a variety of sizes. The size of your specific drill bit will be printed on the flat edge.
The drill bit is shaped like a flat spade with a protruding point at the centre of the upper edge. The point is sharpened to help keep the drill bit steady in the wood. There are 2 sharpened edges on either side of the point which are used to cut through the wood.
There is another version of a flat bit which is known as an expansive bit. It is somewhere between a traditional flat bit and an auger drill bit. It has a special fitting attached to change the size of the drill bit according to the desired size of the hole.
Glass or tile
This type of drill bit is very easily distinguished from all other types. The tip is flat and shaped similarly to a trowel, with no easily discernible cutting edge. The tip is made of a brazed-on carbide and it was initially intended to be used manually, instead of with a drill.
It must be used with a great deal of pressure and a low speed. You must use water to lubricate the cut and cool the drill bit down.
Hexagon shank
There are many versions of these drill bits, including slotted, Philips, and Ponzi drill bits. As well as this, there are designated masonry, metal, and wood versions.
The hexagon shank refers to the end of the drill bit that is inserted into the body of the drill. The shape helps the drill bit to spin less in the chuck or allows it to be used in a magnetic bit holder driver.
Holesaw
These are commonly used with other drill bits and are rarely used alone. Again, there are many different types with different purposes.
Bi-metal hole saw drill bits are used to cut through wood, plastic, sheets of steel, and other metals. Cobalt hole saw drill bits are used for thicker steel and other hard materials. You can also get TCT (tungsten carbide tipped) for even harder materials, and diamond grit hole saw drill bits. These are used to cut slate, ceramics, tiles, and glass.
Multi-construction
These are drill bits that are suitable to use on most material types. The only things that these drill bits cannot handle are tile and glass. The only downside of these drill bits comes if you use them on masonry. This is because the action of drilling through that material will file the cutting edges off of the drill bit. This then means that the drill bit is not effective at cutting through any materials aside from masonry.
Saw
This drill bit has cutting flutes with teeth on both sides. This helps the drill bit to move through the material being cut sideways. This type of drill bit is ideal for soft materials including plastics and wood.
SDS
This is a German creation, invented by Bosch in the 1970s. SDS stands for Spannen Durch System, which translates to clamping by the system. Since then, SDS has come to mean special direct system and is an internationally used abbreviation.
It is a type of push-fit drill bit specifically for use in certain models of masonry drills. Some of these drill bits can penetrate through the rebar material of reinforced concrete.
Spot weld
Again, there are multiple types of spot weld drill bits. The most common is a drill bit guided spot weld drill and a high-speed cobalt drill bit. They are used primarily to drill through thick and hard materials. They are particularly useful for drilling through welded areas of metal, hence their name.
Step drill
This is similar in design and functionality to the cone drill. The real difference is that the steps on the drill bit are parallel to each other, meaning that the hole created will be consistent all around.
TCT precision
This is a tungsten carbide-tipped precision drill bit and is designed to drill through very hard materials. The blades have been highly sharpened on all cutting faces, making them perfect for cutting through hard metals.
How do you clean your drill bits?
It is vital to correctly maintain your drill bits. If you overlook this process then your holes will become steadily less precise and accurate. Drill bits are placed under a huge amount of pressure and operate at very high speeds, making maintenance even more important.
You should aim to clean your drill bits after every use. This will extend their lifespan and ensure your next project goes smoothly.
While using your drill, we recommend switching it off at 5 to 10-minute intervals. You should wipe off the drill bit with a dry cloth to remove any debris each time. This prevents your drill bit from becoming scratched or damaged.
Once you have finished using the drill completely, switch it off and allow it to cool for a short time. Grab a clean and dry cloth and wipe the drill bit from the base to the tip. Keeping your hands clear of the drill bit, spin the drill slowly with the cloth still wrapped around the drill bit.
If there is any stubborn dirt and debris on the drill bit, use a clean and dry toothbrush to scrub it off. This tends to be easier to do with the drill bit still inserted into the drill.
Once you are satisfied with the cleanliness of the drill bit, apply a light coating of machine oil. Place the drill and drill bits away in a cool and dry area for storage. This area should not be exposed to sunlight or the elements.
Tony Moran is a writer, blogger and DIY enthusiast living in rural Norfolk, England, UK, with his wife and a lively border collie. Subscribe to this blog for updates and receive more awesome home improvement tips.
