AS9120B, ISO 9001:2015, and FAA AC 0056B ACCREDITED

What Is a Twist Drill Bit?

Drills are a common type of tool used in a variety of settings, allowing one to produce holes in a surface for fasteners or other components to be implemented. In order for drills to accommodate a wide variety of needs and hardware, a number of drill bits can be procured. Drill bits are simply cutting tools that are able to remove materials to create holes, and the holes they create are based on their cross-section and size. One of the most common types of drill bit is the twist drill bit, that of which can cut wood, steel, plastic, and concrete alike.

A twist drill bit will most often come in the form of a metal rod that features a specific diameter. Along the length, two, three, or four spiral flutes will be present, the exact number being dependent on the intended role of the type of drill bit. For example two-flute twist drill bits are suitable for primary drilling, making them the most popular option. Meanwhile, three- and four-flute drill bit options are typically only used to enlarge cast or punched holes within a production setting.

Between each flute is a section called the web, and the web will have relief grinding carried out to create an angle that is 59 degrees from the drill’s axis. This results in a slipped cutting edge known as a lip at each flute edge. Due to the design of cutting lips, flutes, and other such elements, twist drills require constant clearing that is done by completely withdrawing the bit from the hole. It is important that this is done so that you do not have to manually clean flutes. This can seem time-consuming, but the process of cleaning twist drill bits is much quicker when compared to drill press and drill motors.

When choosing between twist drill bits, one will be offered a number of size options that vary by 1/64 inch increments. Such drill bit sizes are also assigned numbers to make things easier, the number 1 size being .228”, while number 80 bits are .0135”. For fractional diameter sizes, lettered organization is used. While number series increase while size decreases, letter series get larger the further down the alphabet you go. Beyond naming conventions, it is also very important to know that twist drills may also come in metric sizes to ensure that any diameter required is obtainable.

Another important consideration to make when choosing between bits is what attack angle is desired. Generally, the attack angle is determined by the rate of twist that the flute exhibits. Many drill bits are designed to be optimal for use on steel, and these bits generally work well for wood too. However, these bits are not well-suited for non-ferrous metals like brass and copper, meaning that another attack angle will be required to prevent mishaps and injury. As twist drill bits are known for making very accurate diameter holes, make sure to find the right fit for your needs and start the purchasing process with After Market Aviation Spares today!

After Market Aviation Spares is a premier purchasing platform that belongs to the ASAP Semiconductor family of websites, and we are unmatched in our ability to meet customer needs with highly competitive pricing and rapid lead times. Explore our website as you see fit, and note that all listings on our website can be purchased at any time. If you find any items of interest, make sure to fill out and submit an RFQ form with as much information as you can. Once our team receives and reviews your request, they will reach out in 15 minutes or less to provide a customized solution based on your needs. See how After Market Aviation Spares can serve you when you get in touch with a team member!


January 19, 2024

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