Stjärnskruv

Stjärnskruv is a Swedish term referring to a type of screw head designed with a cross-shaped recess. This recess is specifically shaped to accommodate a corresponding screwdriver tip, also known as a Phillips head screwdriver. The design allows for a more positive engagement between the screw and the driver compared to older slotted screw designs, reducing the likelihood of the screwdriver slipping out of the recess, a phenomenon commonly referred to as cam-out.

The stjärnskruv, or Phillips head screw, was invented by Henry F. Phillips in the 1930s. His innovation aimed to improve the efficiency of mass production, particularly in the automotive industry, where automated screw driving was becoming increasingly important. The specific geometry of the recess was patented, and it became widely adopted due to its effectiveness.

While the stjärnskruv is very common, it has some limitations. Under high torque, the screwdriver can still cam out, potentially damaging the screw recess or the workpiece. This led to the development of alternative screw head designs like Pozidriv, which offers even better resistance to cam-out, and Torx, which provides superior torque transfer. Despite these advancements, the stjärnskruv remains a prevalent fastener in many applications due to its ease of use and widespread availability of compatible tools.