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The anatomy of drill bit: drill bit parts

Mar 23, 2016

Before we begin, lets make it very clear that different specialist drill bits are designed slightly differently. However, for our purposes we are looking at the common, basic HSSS [high speed straight shank] bit that is usually found in hardware stores for home do-it-yourself or electric drill kit sets.  Drill bits are made either from high speed steel [HSS]or carbon steel, the latter predominantly used for boring in wood. Carbon steel bits are also brittle and more likely to break than HSS, especially in smaller diameters.
In the above image [courtesy of http://www.mfg.mtu.edu] we can see the main cutting area of the drill is “fluted,” this gives rise to the term TWIST BIT, a common name for this type of bit. You will find most bits follow this style no matter they be designed for boring holes in wood, metal, plastic or concrete. The twist not only helps the bit bore its way into the material but also acts as a conveyor by removing the debris. On large scale or commercial operations a cooling medium maybe added via the flutes to help prolong the life of the bit.

The TIP of the bit is the major initial cutting part and in some bits, notably wood, [link to wood bits] it is more pointed or needle like. This is often known as the PILOT. This helps penetration and keeps the bit on track. The angle or BITE of the bit varies across different bits depending on their application. The wider the diameter of the bit, generally, the less point there is. On MASONRY [link to masonry bits] this end is tipped or dipped in a hard substance, usually a tungsten carbide, sheath to give the bit a sharper, longer lasting cutting performance. Drills may also be tipped with diamond for extra hard applications or other enhancements, such as those used for drilling it to glass.

The non cutting part of the bit or shank is inserted into the chuck of the drill. In the illustration it is shown TAPERED, but most conventional bits today are sold with a STRAIGHT shank and are easily centred into the chuck of a modern electric drill. Other bits may come with a hexagonal shank to make fitting into a cordless drill easier. This style of bit may also be used with a hand brace. Other shanks are THREADED for use in high performance manufacturing or engineering workshops.
Although the majority of bits on the consumer market are designated “right hand cutting” bits also come in left hand cutting varieties for some specialised engineering purposes.
We hope you found this beginners guide to drill bit parts useful.

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