How Many Types of Shanks Exist for Drill Bits

The shanks of drill bits are fundamental elements for the structure of these tools necessary for drilling metals, wood, and any other material. If you want to best manage the power of this power tool, which you find in any workshop and often also in car boxes, you can't ignore the fact that there is a sharpened section capable of making holes suited to your needs.

Then there is another part of a drill bit that instead connects to the chuck, you don't see it but it does its job to ensure the transmission of rotation. So, here's what you need to know about your bit's shank and what are the different types you can choose.

What is the Shank of a Drill Bit: Definition

Anyone who has used a drill knows the shank of a drill bit. From a technical standpoint, we can say that this is the smooth section of the bit necessary for drilling that is tightened in the chuck. As simple as it is, its role is fundamental to the work to be performed. This could be drilling reinforced concrete or drilling holes in wood, plastic, or glass.

The shape of the shank varies depending on the size of the hole being made and the effort required to work the material, and as we will see, there are also different shanks that can influence the work but also the choice of drill to use.

The Shank: Why is it so Important for Drilling?

This is the end part of the drilling tool that is tightened in the chuck. Its geometry determines the torque transmission capacity and resistance to radial stresses. An incorrect or poor-quality fit not only causes the bit to slip, but can lead to permanent damage to the chuck jaws or, worse, breakage of the tool.

Remember that there are also bits with reduced shank, so with body flared compared to the cutting diameter. Are these solutions less resistant? No, the resistance of the bit depends on the material (HSS, cobalt, carbide) and the construction quality, not on the size of the shank which can be small but still resistant and well-structured.

How Many Shank Types for Drill Bits Exist?

We said that the shank is the end part of the bit; it is inserted into the drill chuck to firmly secure the tool and transmit its rotation (and any percussion). Not all shanks are the same, there are different types to consider.

Cylindrical Shank (Round Shank)

It is the most common standard for helical bits intended for metal and wood. But also for other common materials. The smooth surface allows perfect centering in the rack or self-tightening chuck: can slip if not tightened well, but in case of overload this condition also serves as a safety system to prevent damaging the drill motor.

Sure, if the shank slips frequently and without real reason there's a problem. This type of shank is not suitable for high torques on large diameters, where a three-flat shank is preferred to avoid unwanted rotations.

Morse Taper Shank

The Morse taper shank (MT or MK, from the original Morse Taper) is the ultimate in terms of friction mechanical coupling, fundamental in high-precision industrial operations on column drills, lathes, and milling machines.

Its characteristic is the self-centering and self-locking geometry: the taper allows the bit to align perfectly with the drill axis under feed pressure, eliminating almost entirely the typical eccentricity factor of jaw chucks.

Hexagonal Shank (Hex Shank)

The hexagonal shank - hex shank or hexagonal shank - is a type of shank with hexagonal cross-section, standardized mainly in the 1/4 inch (6.35 mm) size, used as attachment for drill bits, bits for screwdrivers, and rotating accessories.

The length is variable: 25-30 mm for standard bits, 50-60 mm for extensions. Thanks to its structure, slipping is mechanically impossible and a uniform distribution of stress over 6 surfaces is registered. Another advantage of this structure?

The shank with hexagonal shape (which you can see in the image to the side) allows changing the drill bit or bit with one hand, reducing downtime and speeding up a series of operations in complete safety. But it also has lower concentricity accuracy compared to the cylindrical model.

Other important limitations: the diameter is generally limited to 13-16 mm for transmissible torque reasons, and the system is not suitable for percussion: it only transmits rotation, not axial movement. Furthermore, it requires a dedicated bit holder.

The hexagonal shank does not work on traditional cylindrical chucks without an adapter. Before considering its use, make sure you have everything you need to use this shank. Which has its advantage in repetitive and continuous activities.

Can I use a drill bit with hexagonal shank on a drill with a normal chuck? It's not ideal. The cylindrical chuck can tighten a hexagonal shank, but tightening only occurs on the edges and might not hold well under stress. Better to use an adapter or bits with the right shank to avoid damage to the bits and drill, but also possible injuries.

SDS System (Special Direct System)

Developed by Bosch, the SDS shank is the standard for percussion drilling in the construction sector. While other models only transmit rotary motion, the one we are analyzing becomes fundamental for drills used in heavy work.

The SDS goes beyond and is also used for demolition hammers that do heavy work. Specifically, to be technical in the description, we can say that unlike the cylindrical shank, the SDS system allows the bit to move back and forth.

This happens independently of the chuck, maximizing the impact force. There are alternatives: the SDS-Plus shank has a diameter of 10 mm with two open grooves for the locking balls and two closed ones for torque transmission. It represents the ideal solution for light percussion drills. The SDS-Max type has a diameter of 18 mm and is designed for heavy percussion drills.

Problems Related to the Bit's Shank

Those who use drilling tools for glass, plastic, metals, and wood daily know well that sometimes it's the shank itself that shows signs of failure. In some cases, the surface that allows insertion into the rack or self-tightening chuck shows signs of burning. These are indicators of frequent slipping that not only damages the bit but wears the chuck.

If slipping is persistent, you need to identify the causes: it could be a condition of the chuck not being tightened enough, a cylindrical shank under 6 mm (slips easily), or perhaps worn and/or dirty. Sometimes the fault is with the defective or worn chuck.

Try cleaning the shank and jaws. With small bits, consider using a hexagonal shape. But if the shank is worn, is the bit still good? If the wear is superficial (small scratches), it's not a problem. If the shank is deformed, crushed, or has lost material, the bit slips and can be dangerous. In these cases, it's best to replace it: a bit that pulls out can cause accidents.