Ristipääruuvinväännin

Ristipääruuvinväännin, also known as a Phillips head screwdriver, is a type of screwdriver designed to drive screws with a cross-shaped recess in their head. This design was patented by Henry F. Phillips in the 1930s. The recess features four angled slots that create a cam-out effect, meaning the driver is designed to slip out of the screw head if too much torque is applied. This was an intentional feature to prevent overtightening, which could damage the screw or the material it was fastening.

Phillips head screws and screwdrivers are widely used in various applications, including electronics, automotive, and construction. They are often favored for their ease of use and the ability to self-center the screwdriver in the screw head. However, the cam-out feature can sometimes be a disadvantage, especially when dealing with stubborn or rusted screws, or when high torque is required.

There are several sizes of Phillips head screwdrivers, identified by numbers such as PH0, PH1, PH2, and PH3, with larger numbers indicating larger screws and correspondingly larger screwdriver tips. Using the correct size screwdriver is crucial for optimal performance and to prevent damage to both the screw and the tool. In some instances, a Pozidriv screwdriver, which has additional smaller slots, may be mistaken for a Phillips head. While visually similar, they are not interchangeable and using the wrong type can strip the screw head.