Drill bits. One of the most useful and versatile tools that exist. You may be surprised to know that using the wrong one can not only hinder production, but could be costing more than you may think. That’s why it’s important to choose drill bits that are optimized for the application. Otherwise, you’re likely to be replacing the bits and the tools too often. Not only that, but you risk damaging the workpiece and having to start over.
Machinists and fabricators use drills daily, and proper drill bit selection can save both time and money. If you are looking to get the best machining result, here are some things to consider when choosing a drill bit for your next project.
What are Drill Bits Used For?
Drill bits are designed to drill holes in a variety of different common materials. These include different types of wood, metal, plastic, ceramic tile, porcelain and concrete. Drill bits made for steel, aluminum, copper, cast iron, sheet metal, fiberglass, brick, vinyl flooring and more are also available.
Sized for their diameter, drill bits are constructed in a range of styles to help with specific tasks. Not sure which drill bit you need or what you need in your toolbox? Keep reading for a rundown of the different types of drill bits you’re likely to come across.
Materials & Coatings of Drill Bits
There are numerous types of drill bits. To help you understand them better, we shall first discuss the construction of different bits:
Drill bits are made from different materials to suit their purpose. Using the right bit material enhances your efficiency. It also prevents you from losing money, purchasing a drill bit that cannot handle your project.
While almost all bits are made from metal due to its toughness, the difference comes in the metal composition. The following are some common materials used in drill bits.
High-speed steel (HSS) is one of the most commonly utilized materials in the manufacture of drill bits. It is suitable for drilling wood, plastic, and soft metals. High-speed steel bits are made from carbon steel with chromium and vanadium additives.
Thanks to cobalt’s immense structural strength, cobalt drill bits are especially adept at drilling through stainless steel and other tough materials. Cobalt alloys have an exceptional ability to withstand heat and resistance. Sometimes, these drill bits consist of an alloy of cobalt and HSS. Such an alloy guarantees you a bit that can go through just about any surface.
Carbides are one of the strongest substances on the planet. In fact, some carbides rival diamonds for the hardest material known to man. They are formed when carbon is combined with metal. Nonetheless, carbide is extremely expensive. As a result, it would not be feasible to make an entire bit out of the substance.
This is why manufacturers prefer making only the tips out of carbide. Carbide-tipped bits are typically used for masonry, tile, and concrete drilling.
When handling projects involving extremely tough materials, it would be a good idea to consider solid carbide bits. Unlike carbide-tipped bits, solid carbide bits consist entirely out of carbide.
You can also classify drill bits according to the coating they have. They include:
- Black Oxide: helps the bit to retain lubricants to prevent the onset of rust.
- TiN Coated: TiN refers to titanium nitrate, which slows the progression of wear on bits that drill hard metals
- TiAIN Coated: titanium aluminum nitrate coating increases a bit’s resistance to abrasion and heat
- SG Coated: a silicone multilayer that helps a drill bit to penetrate dense metals.
Types of Drill Bits
1. Flat Drill
This type of drill is generally made by beating slender sticks of high carbon steel. Their cutting edge is ground and then hardened and tempered. It can be made easily in any shape or size. These are made in different sizes after forging them. These drills are very cheap.
It is not used for boring holes in iron. It is usually used for boring holes in carpentry work and soft metals. The cutting point is kept at a 90° angle. On those solid metals where other drills get broken, this drill can be used after properly hardening and temping.
2. Straight Fluted Drill
A straight fluted drill consists of grooves or flutes running parallel to the drill axis. A straight fluted drill can be thought of as a cutting tool with zero rakes. This type of drill is not available in standard practice as the chips do not automatically pop out of the hole.
They are essentially used in drilling brass, copper, or other softer materials. In drilling brass, the twist moves faster than the rate of the drill feed, and the drill digs into the metal. There is no such difficulty in using a straight fluted drill.
3. Twist Drill Bit
Nowadays, twist and thick drills are used for boring holes quickly, clean, and of accurate size. These are usually made of high-speed steel and thin rods of alloy steel.
Then cutting edge is made on the bottom end and a twisted groove is cut on its body from top to bottom which is known as a flute. Because of the twisted flute, it is called a twist drill. It contains the main parts such as tang, shank, body, point, and neck.
4. Brad-Point Drill Bit
A brad-point bit is designed for boring into wood. The brad at the center of the bit tip helps position the bit precisely for accurate drilling and produces a clean exit point in the work piece. The flutes — grooves that wrap around the bit and channel away chips and dust — are extra-wide to remove more material.
5. Auger Drill Bit
An auger bit, another type of wood-boring bit, has a screw tip that starts the hole and pulls the bit through the work piece to quickly create a clean hole. These bits can be as long as 18 inches. As with the brad-point bit, large flutes help remove chips and dust. An auger bit with a hollow center provides even more chip removal, allowing for deeper boring; one with a solid center is stronger and more rigid.
6. Forstner Drill Bit
A Forstner bit bores smooth, clean holes in wood. You can use it to create flat-bottomed holes for receiving dowels. If you need to bore through the work piece, it creates a neat exit hole. The design also allows you to overlap holes. A point helps you to position the bit precisely on the work piece. Pull the bit out regularly to clear away chips and dust as you work. A handheld drill may not always give you the force or control you need to use a Forstner bit, so a drill press is a better option for some applications.
7. Step Drill Bit
A step bit is designed primarily for drilling in thin metal, up to 1/4 inch, but will work with wood. The stepped design allows you to use a single bit to drill holes with different diameters. Often the diameter of each step is etched into the metal drill bit. You can also use this type of bit to deburr holes, clearing away waste material.
8. Countersink Drill Bit
A countersink bit, also called a screw pilot bit, is a specialty bit for drilling in wood. In a single action, the bit can drill pilot, countersink and counterbore holes, allowing you to countersink a fastener and install a plug over the fastener head.
9. Counter Sinking Drill
Countersinking is done by drilling holes in the places where counter head screws are to be installed. In this way, the head job of the screw fits well.
This is a multi-fluted drill in which four flutes are cut. Its cutting point is grinded at 60° or 82°. In the figure, this type of drill and a screw fitted in a hole bored by it has been shown.
10. Brad Point Bits
Brad point bits come in handy when you need to make clean and precise holes. They come with rubber stoppers to allow you to set a particular depth. Their precision makes them a popular bit among woodworkers.
How to Sharpen a Drill Bit？
Tips for Proper Drill and Drill Bit Maintenance:
- Let the drill bit cool off after you have finished your project.
- Wipe the drill and drill bit with a clean, dry towel or cleaning cloth.
- Use a clean, dry toothbrush to brush off any shavings or other debris that may cling to the tool.
- Apply machine oil lightly with a paper towel or microfiber cloth. Let it sit for a few minutes, then wipe up any excess oil with a new paper towel.
- Inspect drill bits for any extensive damage and remove damaged drill bits from the set so they can be replaced.
- Place drill bits back into their case and store in a cool, dry place.