The slotted drive is one of the oldest screw and drive styles. It is a simple design, with just one straight groove on the head. While it was popular for a long time, the potential for slippage became too much with the increased use of automation. The design enjoys continued use for manual assembly, but other designs have proven more reliable.
The Robertson drive, or square drive, was developed by Canadian salesman Peter Robertson in 1906 to combat the slippage issues that plagued the slotted drive. The Robertson drive is characterized by a square indentation in the head of the screw, which both enhances the surface area to which force is applied by the drive and prevents unwanted slippage.
The Philips Drive
Robertson wasn’t the only person tired of slotted drive slippage. While he was developing his square drive, a businessman named Henry Philips began designing his own solution. The Philips Drive, also known as a cross recessed drive, is designed with a cross or plus-sign embedded in the screw head. Like the Robertson Drive, the Philips Drive offered a secure seat upon which to apply pressure with the drive. The cross design allows for a more secure fit, for better force application, and significantly reduced slippage.
A variation on the Philips Drive, the Pozidriv Drive was created to prevent slippage that became common with Philips Drives used in high-torque applications—particularly noticeable in high speed automated assembly. In 1963, a company named GKN Screws and Fasteners developed a screw and drive combination with additional hash marks embedded into the screw head at a 45 degree angle to each cross section to combat this slippage problem. The additional indentations ensure more stability in high-torque applications with less potential for slippage or stripping.
The six-lobe (or hexalobular) drive is similar to the cross-recessed Philips screwdriver, but with six points instead of four. These points, or lobes, are designed to slope toward the center of the screw, which allows the driver to easily slide into position. The additional surface area provided by the lobes allows the drive to withstand higher torque pressure without slippage. Some Six-Lobe screws are designed with a center pin to prevent tampering. While a Philips screwdriver can be used on standard six-lobe screws, these six lobe pins screws require the use of a specialized six-lobe driver, which makes them more tamper-resistant.
Hex Recess Drive
The hex recess drive looks like a combination of the square Robertson drive and the six-lobe drive. It consists of a recessed hexagon shape and is often seen in modern furniture assembly. While not as secure or tamper-resistant as six-lobe drives, they are user-friendly and allow the user to apply force across a wider surface area. The hex recess drive does not handle high-torque well and will strip if tightened too much.
External Hex Drive
Unlike other types of screws, the external hex drive does not have a recessed shape in which to fit the drive. Rather, the entire head of the screw is hexagonal, and the drive is shaped to slip around the outside and exert pressure on the outer edge of the head. It may also be referred to as a bolt, and is used in a similar fashion.
Quality Drives from APM Hexseal
These are just a few of the many head and drive designs available on the market. At APM Hexseal, our expert hardware specialists offer in-depth knowledge of the design and use of a wide range of screws and drivers. For more on the fascinating history and use of heads and drives from around the world, download APM Hexseal’s eBook, “Don’t Lose Your Head.”