The business end of a bit gets all the attention, but the shank — the part your chuck grips — determines whether a bit even fits your tool. Understanding drill bit shank types helps you buy bits that work with the drills you own.
Round Shank
The most common shank is simply round, matching the diameter of the bit up to a point. A three-jaw keyed or keyless chuck grips it from all sides. Round shanks are versatile and self-centring, but under high torque a smooth round shank can slip in the chuck, which is why some jobs call for a different grip.
Hex Shank
A hex (six-sided) shank resists slipping because the flats give the chuck something to bite. A 1/4 inch hex shank also snaps straight into an impact driver collet and into quick-change chucks, so hex-shank bits and driver bits swap fast. This makes them popular for driving screws and for drilling with impact-rated bits. You will find hex shanks on everything from small twist bits to spade bits and nut drivers, which is why they are a favourite for tradespeople who switch tasks constantly on the job.
- Round: the general-purpose standard for drills of all kinds.
- Hex: anti-slip grip and quick-change; fits impact drivers.
- Reduced: lets a large bit run in a smaller chuck.
Reduced Shank
Large-diameter bits often have a shank turned down to a smaller diameter — commonly 3/8 or 1/2 inch — so a big bit will fit a standard chuck that could not otherwise open wide enough. A reduced-shank bit lets you drill a 3/4 inch hole with a 1/2 inch chuck, for example. The trade-off is a little less rigidity, so keep feed pressure sensible and let the bit cut at its own pace. This design is common on extra-large twist drills and is a cost-effective way to reach bigger holes without buying a heavier-duty drill.
SDS and Taper Shanks
SDS shanks have slots that lock into a rotary-hammer chuck and let the bit slide so the hammer can strike it — the standard for serious concrete drilling. Taper shanks (such as Morse tapers) are found on large industrial bits and drill presses; the cone-shaped shank seats directly into a matching spindle socket, driven by friction and a tang, delivering excellent concentricity for heavy work.
Choosing the Right Shank
Start with the tool you own. A cordless drill takes round and hex shanks; an impact driver needs hex; a rotary hammer needs SDS; a drill press may use round or taper. Then consider the job: high-torque or large holes benefit from hex or reduced shanks that will not spin, while quick fastener work suits hex. Quality American-made bits are ground concentric to the shank, so they run true no matter which style you pick.