STAINLESS STEEL SQUARE DRIVE BITS

Square Drive Bits — The square drive recess, also known as Robertson after its original patent, uses a tapered square socket that grips the bit's matching tapered square tip on all four flats simultaneously, giving a self-centring fit that resists slipping and cam-out far better than cross-point patterns like Phillips or Pozidriv. That self-centring quality is why square drive is the standard choice for decking, timber-frame construction, cabinetry, and general woodworking screws, particularly where the screw needs to be driven one-handed or started without the bit wandering off-centre, and where high torque needs to be transmitted without the bit slipping out mid-drive, as a Phillips bit often will under power. Square drive sizing generally runs from the smallest gauges up through larger sizes matched to bigger timber screws and structural fixings, and unlike the hexalobular or Phillips patterns there's no single dominant ISO standard governing the recess — square drive developed primarily as a North American proprietary format under ANSI conventions and is now widely produced generically, but bit and screw sizing still needs to be checked against the specific range rather than assumed to be universal across manufacturers. It's a standard, non-security pattern: any correctly sized square bit will drive any square-recess screw, with no restricted tooling involved, so it's chosen purely for its driving performance rather than for tamper resistance. As with other driver bits, the tool itself is generally made from hardened alloy tool steel rather than stainless, since resisting wear and rounding under repeated torque cycling matters more for a bit than corrosion resistance does. Most square bits use the standard quarter-inch hex shank covered by ISO 1173, making them interchangeable with ordinary bit holders and power tool chucks. There's no square-drive-plus-pin security equivalent in this range; where tamper resistance is the goal alongside high-torque performance, the Hexalobular + Pin or Hex Socket + Pin security ranges are the appropriate alternative, accepting a different, non-square drive shape in exchange for the added security.

FAQs
What size numbers do square drive bits use?
Sizes are typically labelled from the smallest gauges up to larger structural sizes, with most general woodscrews using the small-to-mid range and bigger timber and construction screws needing a larger, deeper-tapered socket.

Do square bits work well in impact drivers?
Yes, the self-centring, high-contact fit performs well under impact loading, which is part of why square drive became popular for decking and construction screws driven with impact tools.

Does a worn bit lose its self-centring advantage?
A worn or rounded tip loses some of its grip on the tapered flats, increasing the chance of slipping under heavy or one-handed driving, so it's worth replacing bits once they show visible rounding.