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Impact drivers can run screws quickly, but their repeated hammering is hard on ordinary screwdriver bits. The right bit matters most when you’re driving long fasteners, working in dense lumber, or using the tool all day. For occasional assembly, a basic set may be enough; for regular construction work, impact-rated bits are worth the small premium.
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What impact-rated means
An impact driver applies short bursts of rotational force as resistance rises. Impact-rated bits are designed to flex slightly under those blows rather than snap like many rigid bits. They typically have a torsion zone—a narrower section near the shank that absorbs some of the shock. That does not make a bit unbreakable: a worn tip, a crooked screw, or excessive pressure can still damage it.
Use 1/4-inch hex bits marked for impact-driver use. Standard bits may work for light tasks, but can chip or break sooner under repeated impact. Avoid using an impact driver as a substitute for a drill when making holes; use drill bits rated for the tool, and check the manufacturer’s guidance.
Choose by screw drive
Match the bit to the screw head, not just the fastener size. The wrong size can cam out—the bit rides up and slips out of the recess—damaging the screw and often the workpiece. Press firmly in line with the screw, keep the tool square, and slow down as the head nears the surface.
- Torx (star): Common in deck, cabinet, and structural screws. The six-point profile usually holds the bit securely and resists cam-out when the size is correct. T25 is common for many deck screws, but check the screw packaging; sizes vary.
- Square (Robertson): Often used in woodworking and some construction screws. The bit sits snugly in the recess and can be convenient for one-handed starting. Match the numbered size printed on the screw package or bit; a loose fit can round the recess.
- Phillips: Widely used in general hardware and indoor assembly. Phillips heads are designed to cam out under high torque, so they are less forgiving in an impact driver. Use the exact size—often #2 for common household screws—and reduce speed near seating.
Pozi-drive screws look similar to Phillips but have additional ribs between the main slots. A Phillips bit may seem to fit, then slip under load. Use a Pozi bit when the screw is marked PZ or the head has those extra ribs.
Bit types compared
| Drive | Typical strengths | Common failure | Good choice for |
|---|---|---|---|
| Torx | Secure engagement; less cam-out with a correct fit | Wrong size chews the star recess | Decking, framing hardware, and frequent driving |
| Square | Positive fit; useful for controlled starts | Loose or worn bit rounds the recess | Wood screws and jobs supplied with square-drive fasteners |
| Phillips | Easy to find; suitable for light fastening | Cam-out can strip the head quickly | Light assembly and occasional repairs |
What to buy
For mixed household work, start with a small impact-rated assortment containing the sizes you actually use: commonly T20 and T25 Torx, #2 Phillips, and the square-drive sizes specified by your screws. A compact set is easier to keep track of than a large box full of duplicates. If you mainly install one type of fastener, buy a few matching bits rather than relying on a general-purpose set.
Compare impact-rated Torx, square, and Phillips bit sets. Check that the package says impact-rated and includes the drive sizes you need. Sets vary: some contain many short bits but few duplicates, while others include several of the high-wear sizes that are useful on a job.
Long bits help reach recessed screws, but they can flex more and are easier to lever sideways. For everyday fastening, short bits or a bit holder offer better control. If you need extra reach, a quality impact-rated extension is more appropriate than stacking loose extensions.
When a cheaper bit is fine
A basic bit set can be reasonable for occasional furniture assembly, a few small screws, or a cordless drill used at low speed. If the bit fits tightly and the fastener is easy to drive, there is little benefit in replacing it just because it is inexpensive. The case for impact-rated bits is stronger when you regularly drive long screws, work in dense wood, or use an impact driver at high torque.
Buying premium bits does not fix a poor match. A top-quality #2 Phillips bit will still slip in a worn or incorrectly sized screw head. Stop when the bit starts climbing out, inspect the recess, and replace a visibly rounded bit rather than forcing it.
Use bits that last longer
Set the screw straight and maintain pressure along its axis. Start at a lower speed when possible, then increase once the threads have caught. For long screws in hardwood or near board ends, predrill a pilot hole; the needed diameter depends on the screw’s core and the wood, so follow the fastener maker’s chart when available. A pilot hole reduces splitting and lowers the torque that can twist a bit.
Use the tool’s lower speed setting for control, and ease off the trigger as the head seats. Driving until the driver hammers continuously after the screw is already tight wastes bit life and can strip the head, snap the screw, or overdrive it into the material. A clutch-equipped drill can be a better choice for delicate hardware, while an impact driver is useful when speed and high fastening torque matter.
Keep bits clean and replace them when the tip is rounded, chipped, or no longer seats firmly. A worn bit is more likely to cam out and damage a screw than a fresh, correctly sized one. For repeated work, keeping spare T25, #2 Phillips, or other task-specific bits on hand is more practical than waiting for one to fail.