Spårskruvar

Spårskruvar, or slotted screws, are a type of screw characterized by a single straight groove across the head that accepts a flat-blade screwdriver. The drive requires precise alignment of the screwdriver with the slot to apply torque effectively, and cam-out is common if the blade is not kept square to the slot.

Spårskruvar come in various head shapes, including countersunk (flat) heads for flush seating and pan or round heads for protruding applications. They are used with different thread types, such as wood screws with coarse threads for joining timber and machine screws with finer threads for metal or pre-tapped holes. Materials range from carbon steel to stainless steel and brass, with finishes including zinc plating, galvanization, or black oxide to improve corrosion resistance.

In practice, spårskruvar are common in woodworking, cabinetry, and light industry due to their simple manufacturing and low cost. They are easier to produce than more complex drive types, but require careful handling to maintain alignment. For wood, pilot holes or undersized cores help prevent splitting; for metal, appropriate tapping or clearance holes are often necessary. The flat-head design also allows for a countersunk installation in many applications, creating a neat, flush surface.

Advantages of spårskruvar include simplicity, low cost, and wide availability. Disadvantages involve poorer grip under torque compared to cross-headed drives, higher susceptibility to cam-out with misalignment, and potential damage to the slot from tool wear. Despite modern alternatives, slotted screws remain in use where simplicity and cost are prioritized, or in legacy equipment and furniture.