Stjärnskruvar

Stjärnskruvar, known in English as Phillips head screws, are a type of screw characterized by a cross-shaped recess in the head. This recess is designed to accept a corresponding Phillips head screwdriver. The design was patented by Henry F. Phillips in the 1930s, intended to allow for greater torque to be applied without the driver slipping out of the recess, a common problem with slotted screws.

The Phillips system features four slots that form a cross. These slots are slightly tapered, meaning the driver will cam out if too much torque is applied, preventing damage to the screw head or the workpiece. This self-camming action was a significant improvement over previous screw designs. The sizing of Phillips screws and drivers is standardized, with sizes ranging from PH0 (smallest) to PH4 (largest).

While widely adopted, the Phillips head screw has some drawbacks. The cam-out feature, while intended to prevent over-tightening, can also lead to the driver slipping out unintentionally during assembly, especially if the driver is worn or the screw is slightly damaged. This can be frustrating and can strip the recess. For applications requiring very high torque or a more secure connection, other screw head types like Torx or Pozidriv are often preferred. Despite these limitations, the stjärnskruv remains a common and recognizable fastener in many everyday applications.