Screw Drive Types

Screw drive types at a glance

Head shape and drive type are two separate choices. The head decides how the screw seats against the material; the drive decides how you turn it. This page covers drives only. For head profiles such as pan, countersunk and bugle, see the screw head types guide.

Cam-out is the tendency of the bit to ride up and out of the recess under load. Relative torque compares practical torque transfer at the same screw diameter.

Philips vs Pozidriv: how to tell them apart

This is the most common mix-up in fastening, and it costs real money in stripped heads. Both are cross recesses, but they are not interchangeable.

Philips (PH) was designed in the 1930s with tapered flanks that deliberately cam out once a target torque is reached. On hand-built assembly lines that acted as a crude torque limiter and protected the joint. Driven hard with a modern power tool, that same taper is a liability: the bit lifts, chews the recess and rounds it out.

Pozidriv (PZ) keeps the cross but adds four shallow radial ribs set at 45 degrees between the main slots. Those ribs give the bit a near-parallel bearing surface, so it stays seated and transfers noticeably more torque before slipping.

The visual tell: look at the screw head. If you can see four fine tick marks radiating between the arms of the cross, it is Pozidriv. A plain cross with nothing between the arms is Philips. Bits are stamped PH or PZ followed by the size.

Using a PH bit in a PZ screw, or the reverse, contacts only a fraction of the intended surface and is the fastest way to destroy both. If your line runs Pozidriv screws, make sure the bit stock matches.

Torx and why it dominates powered assembly

Torx uses a six-point star with flanks close to vertical. Because there is almost no wedge angle, virtually none of your driving force is converted into the axial force that pushes a cross-head bit out of the recess. In practice that means higher torque, far less bit wear, less operator fatigue and fewer rejected parts from stripped heads.

For any assembly running impact drivers or automated screwdriving, Torx is usually the right specification. It also allows a smaller recess for the same torque, which lets designers use lower-profile heads.

Bit size chart by screw gauge

Match the bit to the recess in the screw, not to the screw diameter alone, since recess size varies slightly with head style. The table below covers the sizes we produce most often.

Typical pairings for standard head styles. Confirm against your drawing where the recess is specified explicitly.

Slotted, square and hex

• Slotted is the oldest drive and the weakest. The bit is not self-centring and slides out of the slot sideways under load, so it suits low-torque, hand-driven and restoration work where appearance matters.
• Square (Robertson) grips the bit well enough that a screw will hang on it unsupported, which makes overhead and one-handed work much faster. It is common in North American joinery and cabinetry.
• Internal hex (Allen) puts a deep six-sided socket in the head. It transfers high torque in a compact, clean-looking head and is standard on socket cap screws to ISO 4762 and DIN 912.
• External hex moves the drive to the outside of the head for spanner or socket driving. There is no recess to strip, so it handles the highest torque of all.

Choosing a drive for your assembly

• Powered, high volume: Torx first, Pozidriv second. Both cut cam-out and bit replacement cost.
• Hand assembly, torque limiting wanted: Philips, where controlled cam-out protects a delicate joint.
• Overhead or one-handed fitting: square drive, for its self-holding grip.
• Maximum torque in a small head: internal hex.
• Appearance-led or heritage work: slotted.

Drives we manufacture

C S Fasteners produces Philips, Pozidriv, Torx, square, internal hex and slotted recesses across our self tapping screws, machine screws, wood screws and chipboard screws. Non-standard, combination and security drives are made to drawing on our custom screw line.

Send us a drawing or a sample and we will confirm the recess, bit size and tooling before production. See also the head types guide, the DIN and ISO standards reference and the finishes guide.