A drill bit shank is the end piece of a drill that connects into the chuck of a spinning mandrel. In essence, it is the male end of the bit that does not drill or mill. As there are many types of drill bits, there is equal variance in drill bit shanks. The primary difference between the shanks is shape, but they can also have functional distinctions.
A brace shank is essentially a multi-sided shank that tapers to a point and locks into a chuck through the angular dispensation. Brace shanks were more popular before modern machining techniques made it easier to construct more complex and durable shank shapes and sizes, because they are not difficult to construct. Torque tolerances are reasonable for brace shanks although stripping can occur, especially if a dedicated chuck is not used.
A very common shank type, a straight shank resembles a brace shank except its tip is not tapered. Instead, the cylindrical tip simply inserts into the chuck flush. Some straight shanks are proper cylinders, while others have angled sides. Round shanks have low torque transmissions, which can help prevent straight shanks from drilling very hard materials. Some drill bits feature straight shanks smaller in diameter than the bit itself, which allows for diversity in chuck size. Straight shanks also don’t require dedicated chucks, which provides for widespread use.
The hex shank is named after the hexagonal shape of the shank, similar to a screwdriver bit. Because of this shape, hex shanks can be used in both dedicated drill mandrel chucks and screwdriver bit chucks. The angled shape of the shank enables the bit to handle higher torque transmissions than brace or straight shanks meaning they can work with material with higher resistance, such as hard metals or geological formations. However, the angle can also cause decentering, leading to less accurate drilling.
The triangle shank is similar to a hex shank in that it is angled, but it only has three angles to the hex’s six. It features many of the same strengths as the hex, including high torque capabilities and good centering. However, it cannot attach to quite as many different drill chucks as the hex.
SDS stands for the German expression “Steck-Dreh-Sitz,” or “Insert-Twist-Stay,” although the English acronym stands for “Special Direct System.” These shanks are specially designed with a spring load installation feature that allows a worker to insert the shank into a chuck by hand. During drilling, the spring gives under pressure, so the drill can perform hammering or masonry activity. Relatively young for a drill shank, the SDS was first produced in 1975, and is more complicated to manufacture than most other shankw. Additionally, the SDS requires a dedicated chuck, eschewing versatility for specific functionality.
Morse taper shank
Morse taper shanks resemble Phillips head screwdriver tips. The shaft is a cylindrical section that terminates in a tapered flat section at one end. Morse taper shanks can only function in dedicated chucks because of this detail. They are relatively easy to produce, but workers need to be familiar with morse taper bits to ensure proper performance. Torque transmission, for instance, can vary if proper procedures aren’t used.
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