ristipääruuvi

Ristipääruuvi, or cross-head screw, is a screw with a cross-shaped recess in the head designed for cruciform drivers. The term is used in Finnish to describe several cross-head styles, most notably the Phillips and Pozidriv families that dominate consumer hardware and fastenings.

Design and function: The cross recess centers the driver and allows relatively high torque to be transferred between tool and screw. Phillips screws are specifically designed to cam out at high torque to prevent overtightening, a feature that facilitated hand and automated assembly. Pozidriv and other modern cross-heads add additional geometry to improve engagement and reduce cam-out, making them easier to drive with less slippage when using the proper driver.

Variants and compatibility: The most common cross-head variants are Phillips (PH) and Pozidriv (PZ). In Japan, JIS cross-head screws are used in many applications and require compatible drivers. Using a mismatched bit can damage the screw head and the driver. Typical drive sizes include PH0, PH1, and PH2, and PZ0, PZ1, and PZ2, with PH2 and PZ2 being common for many consumer fasteners.

Materials and finishes: Ristipääruuvit are manufactured in steel and stainless steel, and may be coated or plated (for example zinc-plated, black oxide, or nickel) to resist corrosion and wear. Head styles and drive recesses can vary slightly by manufacturer, but PH and PZ remain the dominant standards.

Use and applications: Cross-head screws are widely used in furniture, cabinetry, electronics enclosures, automotive assemblies, and various consumer products, where ease of manual or powered driving is advantageous and tool availability is high.