Screw Head Types and Drives: An Eleven by Seven Matrix

Head and drive are separate decisions

Eleven head types — flat, pan, hex washer head, hex washer flange, bugle, wafer, pan washer, oval, flower, truss and round — combine with seven drives: Phillips, square, Pozidriv, square-plus-Phillips, Torx, slotted and Phillips-plus-slotted. They are specified independently, so almost any combination is available.

Choosing the head

Flat and oval countersink flush where a following layer has to pass over. Bugle sinks into board without tearing the facing. Wafer and truss are wide and low, for thin or soft material that a pan head would pull through. Pan washer and hex washer head add a bearing face for thin sheet. Hex washer flange builds the serrated washer into the head, which is what you want under vibration.

Choosing the drive

Phillips is designed to cam out, which was a feature before torque-limiting drivers existed and is a defect now. Pozidriv adds four ribs and grips better. Square transmits high torque and holds the bit on the driver. Torx puts almost no outward force on the bit, which is why it is the recess for powered assembly and for stainless screws that must not be over-driven.

Where the hex head belongs

A hex head is driven with a nut setter, not a bit, and cannot cam out at all. That is why it dominates roofing — and why we also supply the magnetised nut setter sleeve for #6 to #14 heads.

Everything on this page describes the specification range Beyond Industry Groups Limited works to. Where a figure is a laboratory test result rather than a service life, it is described as such.