Torx, 1967: the screw head that stopped cam-out once drivers could limit torque

The Phillips screw's tendency to cam out under high torque was not a defect; its 1930s patent lists it as a feature that spared screw heads and drivers when a hand or crude power tool over-torqued. But on a 1960s factory line, torque-limiting automatic screwdrivers could hit a set torque on their own, and every cam-out event just meant stripped heads, worn tips and scrapped work.

Camcar Textron's answer, filed by Bernard F. Reiland in March 1967 (US patent 3,584,667), was a six-lobed star drive with near-vertical sidewalls. Force transfers along the walls rather than bursting outward, so the driver cannot climb out under load; the head survives more torque than an internal hex of the same size, and tips last longer because no end load is needed to keep the bit seated.

The adoption logic was arithmetic, not marketing: a fastener that never slips and never strips takes fewer rework stations and fewer bit changes. Automotive, IT and consumer-electronics assembly lines moved to it, the drive was standardized by ISO as "hexalobular internal" (ISO 10664), and "star" bits spread everywhere after the patents ran out.

Design the cam-out away instead of relying on slip

It deleted the workaround: once tools could limit torque, the slip-away feature was a cost with no benefit.

Vertical sidewalls convert torque into tangential force, so higher torque needs no bigger, heavier head.

Fewer strippings and longer bit life are line-economics wins a plant manager can count per shift.

One T-series drive fits both SAE and metric threads, shrinking the bits a factory has to stock.

Standards inherit their ancestors' workarounds. When the environment removes the reason for one — here, crude drivers — redesign the interface instead of patching it.

Torx became the standard fastener drive of high-volume assembly — cars, laptops, appliances — with sizes T1 to T100 and external E-series sockets. As the original patents lapsed around 1990, Camcar's successors extended the line with Torx Plus to keep a proprietary edge, and generic six-lobe bits became commodity tool items worldwide. The Phillips screw survives where hand tools and intentional slip still make sense; everywhere a machine drives screws at a set torque, the lobes won.