Hex Drill Bits: Check the Shank, Not Just the Cutting Size

Hex drill bits are worth choosing when quick changes help your work sequence—but the hex shank alone does not tell you what they can drill or whether they are suitable for an impact driver. Check the cutting diameter, holder fit, material application and impact compatibility separately.

Here, “hex” means the six-sided shank held by the tool, not a bit that makes hexagonal holes or an Allen-style screwdriver tip.

Shank size is not hole size

A 1/4-inch hex shank describes the connection to the tool. It does not necessarily mean the bit drills a 1/4-inch hole. For example, Makita’s D-23880 has a 1/8-inch cutting diameter and a 1/4-inch hex shank. The common 1/4-inch connection is 6.35 mm.

Read both dimensions before buying:

• Cutting diameter: the nominal hole size.
• Shank size and profile: what must fit and be retained by the tool.
• Working length: the usable drilling reach, not simply the bit’s overall length.

Bosch lists diameter, total length and working length separately for its EXPERT HEX-9 Multi Construction bits. That distinction matters when a bit must pass through a thick workpiece: extra overall length is not automatically extra drilling depth.

Will hex drill bits fit your tool?

Tool or holder	What to check
Drill/driver with a three-jaw chuck	A suitable hex shank can be clamped in the chuck, provided it is within the chuck’s capacity.
Impact driver with a 1/4-inch hex holder	Choose a compatible quick-change shank and a bit explicitly approved for impact-driver use. Check that the tool is suitable for the drilling task too.
SDS-plus or SDS-max rotary hammer	Match the bit to that SDS system. A hex shank is not a direct substitute.

Bosch confirms that its HEX-9 shanks fit both three-jaw drill chucks and 1/4-inch internal hex holders. It also identifies the hex geometry as providing a more secure connection against slipping than a cylindrical shank. That is a connection advantage, not proof of better cutting performance. Bosch’s compatibility guidance and Makita’s shank-system guide distinguish these connections.

Do not assume every six-sided shank is the common 1/4-inch quick-change format. Verify the dimensions and the tool’s accepted accessory profile. A round shank does not fit directly into a hex-only holder.

Hex does not automatically mean impact-rated

Physical fit and impact suitability are different checks. Look for an explicit impact rating or manufacturer approval for use with impact drivers—not just “hex shank” on the listing.

The DeWalt DCF887 instruction manual specifies 1/4-inch hex accessories and warns that non-impact accessories may break and create a hazardous condition. It also calls for inspection for cracks before use. Check the tool manual’s permitted applications as well: this manual identifies the DCF887’s intended use as impact screwdriving. An impact-compatible bit does not expand a tool’s approved applications.

An impact-compatible drilling bit can still be used in a suitable conventional drill. Makita’s A-97813, for example, is expressly intended for both impact drivers and driver-drills. Buying that connection does not commit you to drilling with impact action.

Choose the cutting end for the material

Two bits with identical hex shanks can have very different jobs:

• General metal, wood and plastic drilling: Makita lists its A-97813 as an HSS twist bit for ferrous and non-ferrous metals, wood, plastic and cast iron. Its black-oxide finish does not turn it into a masonry bit. Manufacturer specifications
• Mixed-material work: Bosch’s carbide-tipped HEX-9 Multi Construction range lists applications including concrete, brick, soft ceramic tile, wood, plastics, sheet metal and aluminium. Those are that range’s stated applications—not capabilities shared by all hex bits. Manufacturer application guidance

For clean wood holes, sheet-metal openings or larger holes, settle the cutting design first using our guide to drill-bit types. For stainless-steel work, compare the material and operating requirements in our cobalt drill-bit guide rather than choosing by shank alone.

When to buy hex instead of round

Choose hex when you regularly alternate between pilot drilling and screwdriving in a compatible quick-change holder, or when you need a manufacturer-approved drilling bit for a suitable impact driver.

Keep suitable round-shank bits if you mostly drill with a three-jaw chuck. There is no need to replace them solely to gain six flats. For work requiring careful drilling-speed and feed control, choose a drill/driver or suitable drill press, then select the bit to match. Holder convenience should not decide the whole setup.

Before changing bits, disconnect the power or remove the battery. Seat the accessory according to the tool manual and confirm that it is retained before starting. Clamp loose workpieces and wear eye protection. Those precautions remain necessary whichever shank you choose. DeWalt’s operating and safety instructions