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The shank is the part of a bit that the drill grips. Match it to the chuck before buying: a bit may have the right diameter and cutting tip yet still slip, wobble, or fail to lock in. Most cordless drills use a three-jaw chuck that accepts round and hex shanks; impact drivers usually use a 1/4-inch hex collet. The key is to check the tool’s chuck or collet, not just the bit’s packaging.
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Identify your chuck or collet
Open a drill chuck and look at its jaws. Three jaws that tighten around a bit indicate a standard three-jaw chuck. Many cordless drills have a keyless chuck, which you tighten by hand; some older or heavier-duty drills use a chuck key. Both can grip round and hex shanks if the shank fits within the chuck’s stated capacity.
An impact driver has a different fitting: a spring-loaded 1/4-inch hex collet. Pull the collar forward, insert a bit with a compatible 1/4-inch hex shank, then release the collar and check that the bit is locked. Some impact drivers accept only insert bits; others also accept longer bits with a groove near the shank tip. Check the manual if the bit does not seat.
Common shank types and what they fit
| Shank type | Typical fit | Best use | Watch out for |
|---|---|---|---|
| Round | Three-jaw drill chuck | Twist bits, brad-point bits, hole saw arbors | Can slip if the chuck is loose or the shank is oily |
| Hex, usually 1/4 inch | Three-jaw chuck or compatible 1/4-inch collet | Driver bits, some drill bits and quick changes | Not all hex bits lock in every impact-driver collet |
| SDS-Plus | SDS-Plus rotary hammer | Drilling masonry with a rotary hammer | Does not fit a standard drill chuck directly |
| SDS-Max | SDS-Max rotary hammer | Heavy masonry and demolition work | Much larger system than SDS-Plus; not interchangeable |
| Reduced shank | Chuck sized to fit the reduced section | Large bits whose cutting diameter exceeds chuck capacity | Shank may be gripped securely while the bit still demands too much torque |
Match the bit to the tool and job
For a standard cordless drill, choose a bit with a shank diameter within the chuck’s capacity. A chuck marked 1/2 inch can grip shanks up to 1/2 inch; a 3/8-inch chuck cannot safely hold a 1/2-inch shank. Chuck capacity is about the shank, not the hole diameter. A large hole saw or auger may have a smaller reduced shank specifically to fit a smaller chuck, but the drill still needs enough torque for the cut.
Round shanks are a sensible, often cheaper choice for ordinary drilling. They are common on wood and metal twist bits, and a well-tightened three-jaw chuck holds them securely for typical household work. Hex shanks make sense when you change bits often or want to use a compatible impact driver. They resist turning in a three-jaw chuck, but that advantage does not make every drill bit suitable for impact use.
Impact drivers deliver short, forceful rotational blows. Use bits labeled for impact use when drilling or driving with one; ordinary brittle bits can break, especially under side load. For a cordless drill, standard bits are generally fine. If you need a set for both tools, look for 1/4-inch hex bits explicitly rated for impact use, and confirm they fit the driver’s collet.
For masonry, use a masonry bit in a drill’s three-jaw chuck for light work, such as a few holes for wall anchors. For repeated or larger holes in concrete, a rotary hammer with the matching SDS system is usually faster and puts less strain on your hands and drill. SDS-Plus bits fit SDS-Plus tools, not SDS-Max tools or ordinary drill chucks. A chuck adapter may let an SDS tool hold a round bit, but it does not turn a rotary hammer into a good substitute for a regular drill; check the tool instructions and use the correct mode.
Check the fit before drilling
Wipe dust and oil off the shank, insert it far enough for all three jaws to grip, and tighten the chuck firmly. On a keyless chuck, use both hands if the design calls for it; do not rely on the motor to tighten or loosen the chuck unless the manual says that is acceptable. Run the drill briefly at low speed while holding it clear of the work. If the bit wobbles, stop and reseat it. A bent bit, unevenly tightened jaws, or a shank gripped too near its tip can all cause wobble.
A bit that spins in the chuck can burn or score its shank and damage the jaws. Stop rather than increasing pressure. Clean the shank and chuck, retighten, and check that the bit is within the chuck’s capacity. If the bit repeatedly slips during a demanding cut, the chuck may be worn—or the bit and task may be a poor match for that drill.
What to buy
If you own a three-jaw drill and mostly make holes in wood, plastic, or thin metal, buy round-shank bits sized for your chuck. A basic round-shank drill bit set is usually the economical choice. Pay for a wider size range or better bit material only if your work needs it; a budget set is fine for occasional household holes, but cheap bits may dull sooner in hard metal.
If you use an impact driver for both fastening and occasional drilling, a 1/4-inch hex drill bit set rated for impact use offers quick changes without an adapter. It is not automatically the best buy if you already have a drill and rarely switch bits. For concrete or masonry work beyond a handful of small anchor holes, consider an SDS-Plus rotary hammer and compatible bits rather than forcing a standard drill through the job.
Before ordering, compare the bit’s shank diameter and style with your tool’s manual or chuck markings. If the shank fits but the tool strains, overheats, or repeatedly stalls, the problem is likely the bit size, material, or drilling method—not a need to tighten the chuck harder.