Screwdriver bits are not interchangeable, and using the wrong type is one of the fastest ways to strip a screw or wear out a bit. The recess in a screw head is engineered for a specific driver shape, and each design behaves differently under torque. This guide explains the main bit types, how to tell them apart, and which ones matter for different markets.

Why Do Screwdriver Bit Types Matter?

Using the wrong bit damages both the bit and the screw head. Each recess shape is designed for a particular balance of torque transfer, self-centering, and resistance to cam-out, which is the tendency of a bit to slip up and out of the screw under load. A driver that almost fits, such as a Phillips bit in a Pozidriv screw, contacts only part of the recess, concentrating force on a few points and rounding off the head. Matching the correct bit type and size protects the fastener, the tool, and the work.

Screwdriver Bit Types at a Glance

The six most common bit types can be identified by the shape of the recess they fit. The table below summarizes each as a quick reference, and the sections that follow explain them in more detail.

The Main Screwdriver Bit Types

Slotted (Flathead)

The slotted drive is the oldest type, with a single straight groove across the screw head. It has no self-centering ability, so the bit can slip sideways out of the slot under load, which limits the torque it can handle. Despite this, it remains in use for electrical terminals, simple hardware, and applications where low cost matters more than grip. Slotted bits are sized by blade width and thickness rather than by a number.

Phillips (PH)

Developed by Henry F. Phillips in the 1930s, the Phillips drive uses a tapered four-point cross that centers itself in the screw head. It tends to cam out at high torque, a trait that on early assembly lines helped prevent overtightening. That same behavior is its main drawback today, since under heavy load the bit lifts out of the recess. Phillips is the most widely used drive worldwide, common in electronics, appliances, and general assembly. Sizes run from PH0 up to PH4, with PH2 the most common.

Pozidriv (PZ)

Pozidriv was developed in the 1960s as an improved Phillips, built to solve the cam-out problem. It keeps the main cross but adds four smaller ribs set at 45 degrees, creating eight contact surfaces with straighter walls. The result is higher torque transfer and far less slipping, with less downward pressure needed to keep the bit seated. The quickest way to spot a Pozidriv screw is the four small tick marks between the arms of the cross. Phillips and Pozidriv are not interchangeable: a Phillips bit cams out of a Pozidriv screw, and a Pozidriv bit will not seat properly in a Phillips screw. Pozidriv is widely used in Europe, especially in construction and electrical work. Sizes run from PZ0 to PZ5.

Torx (Star)

Torx, whose formal name is hexalobular internal (ISO 10664), uses a six-point star recess. Because the driving force is applied nearly perpendicular to the lobe walls, Torx transmits much higher torque than a cross drive and almost eliminates cam-out, which also extends bit life. Its star shape is mechanically distinct, so it cannot be forced into or confused with a cross recess. Torx is common in automotive work, electronics, and appliances, and its use is growing in construction and other sectors. Sizes are written with a T followed by a number, from T1 to T100, with T10 through T30 the most common. A tamper-resistant version with a pin in the center is used in security applications.

Hex (Allen)

The hex drive uses a six-sided recess turned by a hex key, often called an Allen key, or by a hex bit. It offers strong torque transfer and good resistance to cam-out in a simple, low-cost shape. Hex is the standard for flat-pack furniture, bicycles, and many machinery and equipment fasteners. Hex sizes are measured across the flats and come in both metric and SAE ranges, so both systems are worth carrying depending on the market.

Robertson (Square)

The Robertson drive uses a square recess and was invented in Canada. Both the recess and the bit have a slight taper, so the screw grips the bit and stays on it, which allows genuine one-handed driving and reduces cam-out. Robertson is the dominant drive in Canada and is common in woodworking, decking, and electrical work, with adoption growing elsewhere as older patents expire. A distinctive feature is that its sizes are color-coded for quick identification, running from #0 to #4.

Which Bit Types Should Distributors Stock?

Phillips and slotted bits are universal staples, while demand for the other types depends heavily on the target market. A core range should always cover Phillips, especially PH2, along with a few slotted sizes, since these appear almost everywhere.

Beyond that core, the right mix follows the destination market. A distributor selling into Europe needs Pozidriv as a default rather than an add-on, while Robertson belongs in any range aimed at the Canadian market. Torx is the one type worth carrying almost everywhere, since its use keeps expanding, and a span from roughly T10 to T40 covers most demand. Hex is worth stocking in both metric and SAE, since the right system depends on where the equipment it fits was built.

Bits are sold both in mixed sets and as individual replacements. The higher-torque types in particular benefit from tougher bit material such as S2 steel, which resists the shock of power drivers better than standard chrome vanadium.

Summary

The six common bit types divide into the cruciform drives (Phillips and Pozidriv), the cam-out-resistant drives (Torx, Hex, and Robertson), and the basic slotted drive, each with a recess engineered for a specific job. The two rules that prevent most damage are simple: match the bit type to the screw, and match the size.

KAFUWELL produces screwdrivers and bit sets covering the common drive types, in both individual sets and mixed assortments, in metric and SAE sizes. For piece counts, size ranges, and packaging options, see our product catalog.