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The right bit depends on the screw drive
For stainless steel screws, a well-fitting driver bit matters more than a fancy coating. Stainless fasteners are often used in deck hardware, trim, and other jobs where a stripped head is difficult to replace. The metal is not inherently harder to drive than ordinary steel, but stainless screws can gall or seize in their mating material, and damaged drive recesses leave little room to recover.
Start by matching the bit to the screw: most common choices are Phillips, square (Robertson), Torx (star), and hex. Check the packaging or test the bit in an unused screw. It should seat fully, with little side-to-side movement. A loose fit concentrates force on the edges of the recess and makes cam-out—when the bit climbs out under load—more likely.
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Compare common bit types
| Drive type | Typical use | Strengths | Trade-offs |
|---|---|---|---|
| Torx / star | Decking and many exterior screws | Good engagement and resistance to cam-out | Requires the exact size; nearby sizes may seem to fit but can damage the recess |
| Square / Robertson | Wood screws and some hardware | Holds the screw on the bit and drives steadily | Size must match; a worn or undersized bit can round the socket |
| Phillips | General-purpose screws | Common and inexpensive | Designed to cam out under excess torque, so it is less forgiving in demanding driving |
| Hex | Machine screws and selected construction fasteners | Positive engagement when precisely matched | Can round if the bit is loose or the fastener is driven at an angle |
For new exterior woodwork, Torx is often the easiest drive to control, provided the screw manufacturer specifies it. Square drive is also a solid choice. If you already own Phillips stainless screws, there is no need to replace them for a small job; use a fresh, correctly sized bit and keep the tool aligned with the screw.
What to buy
Buy the drive size printed on the screw package, not a generic assortment and a guess. A short bit is usually more stable than a long one, while a longer bit helps reach recessed fasteners. For an impact driver, choose a bit marked for impact use; these are designed to tolerate repeated twisting loads better than ordinary brittle bits. A set of impact-rated Torx and square bits is a practical choice if you install several screw types.
For occasional repairs, a basic bit that fits correctly is fine. Premium bits may last longer in repeated use, but they do not compensate for the wrong size, poor alignment, or excessive torque. Replace a bit when its tip is rounded, chipped, or visibly polished at the contact points. A worn bit can damage several screw heads in a row.
For a cordless drill, a standard insert bit in a bit holder is usually enough. With an impact driver, use a short impact-rated bit or a suitable impact-rated holder. Avoid using a long, flexible extension unless access requires it: extra length can wobble and makes it harder to keep the bit square. See impact-rated Torx bits when the job calls for that drive style.
Prevent galling and broken screws
Stainless-on-stainless threads can gall: friction causes the surfaces to bind, sometimes abruptly. This is more likely when driving quickly, using high torque, or forcing a screw into a tight or poorly prepared hole. A seized screw may snap even when the drive bit is still in good shape.
In wood, follow the screw maker’s guidance for pilot holes. As a practical starting point, pilot-hole diameter should be close to the screw’s root diameter in dense hardwood and smaller in softwood; the exact size varies with the fastener. For a thick screw near an edge, or a screw entering hardwood, drilling a pilot hole reduces splitting and driving torque. A clearance hole through the first piece can also help pull two boards together rather than letting the screw threads grip both.
For stainless machine screws or stainless fasteners threading into metal, use the specified hole and thread size. If the application allows it, a compatible anti-seize compound can reduce galling, but it changes friction and can affect torque-controlled joints. Follow the hardware or project instructions rather than adding lubricant by default.
Set up the tool and drive steadily
Use a drill’s clutch for small or delicate work, starting low and increasing only if needed. Set the speed to low or moderate, hold the tool in line with the screw, and apply steady pressure. With an impact driver, short trigger pulls give better control than holding the trigger until the screw is buried. Stop when the head is seated; driving farther can strip the recess, crush wood, or snap the screw.
For deck boards, a depth stop or consistent clutch setting can keep heads even. Test the setting on a scrap or hidden spot first. If a screw stalls, do not lean harder on the tool: back it out if possible, check for a pilot hole, debris, a mismatched bit, or a screw that has begun to bind. A pilot drill bit set can help prepare holes across several screw diameters.
If the head starts to strip
Stop as soon as the bit begins slipping. Re-seat it, confirm the size, and try a fresh bit with firm axial pressure. Repeatedly running the tool over a damaged recess usually makes extraction harder. If the screw is already partly seated and the work permits it, reverse slowly while keeping the bit aligned; avoid high-speed impacts on a damaged head. For valuable or exposed work, it is often better to remove a suspect screw early and replace it than to leave a weak, partly driven fastener in place.