Drill Bits for Impact Drivers
An impact driver only takes 1/4-inch hex shanks, and its hammer blows punish brittle steel. Some drill bits thrive in it. Others break in seconds.
We research tools from manufacturer specs and long-term owner feedback. If you buy through our Amazon links we may earn a commission at no extra cost to you. How we make money.
The best drill bits for an impact driver have a 1/4-inch hex shank and an impact rating. Use impact-rated hex twist bits for pilot holes in wood and thin metal, and hex spade or auger bits for bigger holes in wood. Step bits work in thin sheet metal at low speed. Skip masonry bits, large hole saws and anything with a round shank. For holes over about 1/2 inch in metal, or any precise hole, use a drill.
On this page
What makes a drill bit work in an impact driver
Two things decide it. First, the shank: an impact driver has a 1/4-inch hex collet, not a three-jaw chuck, so only hex-shank bits fit. Second, the steel: once the bit meets resistance, the driver starts hammering in the rotational direction, and brittle bits crack under those spikes. A bit sold as impact-rated or impact ready has a tougher shank and often a stronger joint where the hex meets the flutes.
An impact driver drills well when the bit cuts freely and the driver barely impacts. It drills poorly when the bit grabs, because the hammering starts and control gets choppy. If you are still deciding whether to drill with it at all, start with can you drill with an impact driver.
Drill bits for impact drivers: suitability by type
| Bit type | Material | Suitability | Notes |
|---|---|---|---|
| Impact-rated hex twist bit | Wood, plastic, thin steel, aluminum | Excellent | The core set. Pilot holes and clearance holes |
| Standard hex twist bit | Wood, soft materials | Fair | Works, but shanks snap under impact |
| Brad-point hex bit | Wood | Good | Clean entry for furniture and dowel holes; easy to burn if run too fast |
| Spade (paddle) bit | Wood | Excellent | Fast holes through studs and joists |
| Auger / ship auger | Wood | Good to excellent | Self-feeds; can grab hard in knots |
| Step bit (hex) | Sheet metal, plastic | Good | Thin material only, low speed |
| Countersink combo bit | Wood | Excellent | Pilot and countersink in one pass |
| Small hole saw on hex arbor | Thin wood, drywall | Fair | Small diameters and thin stock only |
| Masonry bit | Concrete, brick | Poor | No forward hammer action; use a hammer drill |
| Large hole saw, Forstner bit | Wood | Poor | Chatters and binds; use a drill |
Hex shank twist bits for wood and metal
Impact-rated hex twist bits are the set to buy first. They drill pilot holes for screws, clearance holes for bolts, and holes through light-gauge steel such as strut, brackets and electrical boxes. Most major brands sell them, for example DeWalt Impact Ready and Milwaukee Shockwave lines, with black oxide, titanium-coated or cobalt versions.
- Black oxide or titanium-coated: fine for wood, plastic and mild steel.
- Cobalt: better for stainless steel and harder metals, but more brittle. Choose impact-rated cobalt only.
- Sizes to start with: 1/16 to 1/4 inch covers most pilot holes. 1/8, 9/64 and 5/32 inch get the most use.
Hex bits come in two formats. One-piece bits have the hex ground into the bit itself. Two-piece bits clamp a round bit into a hex collar. One-piece bits run straighter; two-piece bits let you replace just the cutter. The main impact driver bits guide covers the screwdriving side of the kit.
Impact-rated hex drill sets on Amazon Countersink bits
Spade and auger bits for wood
For holes from about 3/8 inch up in framing lumber, spade and auger bits are where an impact driver shines. They cut aggressively, the driver keeps spinning when the bit loads up, and you avoid the wrist kick a drill gives when a big bit binds. Threaded-tip spade bits pull themselves through the wood, which suits an impact driver well. Technique, sizes and blowout prevention are in spade bits for impact drivers.
Augers are better for deep holes through doubled plates and posts, because the flutes clear chips. They can grab hard on knots, so keep a firm grip and start at a slower speed.
Step bits, hole saws and what to avoid
Hex step bits work for knockouts and holes in thin sheet metal, plastic boxes and panels. Run them at the lowest speed setting with light, steady pressure, and let the tool do the cutting. High speed burns the edges and the impacts can grab the bit as each step breaks through.
Hole saws are a stretch. Small saws in thin material can work on a hex arbor, but large saws chatter and bind. The limits are in using a hole saw with an impact driver.
Avoid these in an impact driver:
- Masonry bits. The impact is rotational, not forward. See hammer drill vs impact driver.
- Forstner bits and large hole saws. They need smooth, steady torque.
- Non-impact bits on hard jobs. They snap at the shank. See impact-rated vs regular bits.
- Round-shank bits in a chuck adapter for anything more than light use.
A sensible starter kit
Most homeowners and many trades can cover nearly every drilling job an impact driver should do with a short list:
- An impact-rated hex twist set from 1/16 to 1/4 inch, with spares of 1/8 and 5/32 inch.
- Two or three countersink bits matched to #8 and #10 screws for trim, cabinets and decking.
- Spade bits in 3/4, 7/8 and 1 inch for running cable, pipe and conduit through framing.
- One hex step bit if you do electrical or sheet-metal work.
Anything beyond that, especially big-diameter cutters, belongs in a drill. A big mixed set full of sizes you never use is not a bargain.
How to drill cleanly with an impact driver
- Pick a low or middle speed. Full speed overheats small bits and tears wood fibers.
- Center punch metal. Twist bits wander on bare steel without a starting dimple.
- Start the hole before the driver starts impacting. Light pressure, let the bit bite, then add pressure.
- Keep the driver straight. Side load is the main reason hex bits snap at the shank.
- Ease off at breakthrough. In metal, the bit grabs as it exits. In wood, slowing down cuts tear-out.
- Back out often in deep holes to clear chips, and add cutting oil on metal.
Safety: wear eye protection when drilling, especially in metal where chips and snapped bits fly. Clamp small workpieces instead of holding them; a grabbing bit can spin the part.
When to use a drill instead
An impact driver is a capable backup drill, not a replacement. Use a drill/driver when you need precise, round holes, holes larger than about 1/2 inch in metal, Forstner or large hole saw work, or anything in masonry. A drill also has a clutch and a chuck that takes any shank. The trade-offs are laid out in impact driver vs drill, and the collet itself is explained in impact driver chucks and hex collets.
Frequently asked questions
Can you put a round-shank drill bit in an impact driver?
Not directly. The collet only holds 1/4-inch hex shanks. You can fit a small keyless chuck adapter with a hex shank, but it adds wobble and is not designed for heavy hammering. For regular drilling, buy hex-shank bits or use a drill.
Can an impact driver drill into concrete?
Not usefully. Its blows are rotational, not forward like a hammer drill, so a masonry bit just rubs and overheats. A few soft blocks or mortar joints may work slowly, but for concrete use a hammer drill or rotary hammer.
What size pilot hole bits should I own?
A set covering 1/16 to 1/4 inch handles most pilot holes for wood screws, hinges and hardware. The most-used sizes are usually 1/8, 9/64 and 5/32 inch, so buy spares of those or a set with doubles.
Why do hex drill bits snap at the shank?
Most snap where the hex meets the round body, often from side-loading the bit, using a non-impact bit, or the bit binding as it breaks through metal. Hold the driver straight, ease off at breakthrough and use impact-rated bits.
Are cobalt hex bits worth it for an impact driver?
For drilling harder metals such as stainless steel, cobalt is the better material, but cobalt is also more brittle. In an impact driver, look for cobalt bits that are specifically sold as impact-rated, and drill at low speed with steady pressure.