Styles of Phillips Screwdrivers

Original Phillips Head

• Designed with four sloping arms, slightly rounded corners and a 57-degree drive bit tip, the original Phillips head helps prevent screw stripping. Excess torque applied to the screw causes the driver bit to cam out, or slip out, of the head instead of ruining the recess or the drive bit head. The screw design, established by the American Screw Company in 1934, became the screw of choice on assembly lines (used in more than 85 percent of factories) by the mid-1940s.

Pozidriv

• GKN developed the Pozidriv Phillips screw, shortened from the term "positive drive," in the 1960s. It differs from the original Phillips in that it has a flatter bottom and steeper side walls for use in high-torque applications where cam out is undesirable. A Pozidriv screw is identified by its four additional tick marks between the main slots and the square corners. The driver bit for Pozidriv screws has a blunt end for better seating on the flat bottom of the screw head.

ACR

• Developed for the avionics industry, anti-camout ribs (ACR) screws and drivers have special ribbed sides that provide better mating between screw head and driver bit. Better mating is an important characteristic; avionic panels require removal and reinsertion often for maintenance and repairs. The ribbed nature of the screw and driver bit also translates to less effort to remove the screw. ACR screws are also compatible with original Phillips drivers.

Moretorq

• The Mortorq head is shaped like a windmill with a rounded and flat side to each slot arm. The head is considerably more shallow than other Phillips heads, making it ideal for low-profile applications. The flat sides of the head mate directly with the flat edge of the driver bit to provide maximum torque with zero cam out. The wide, shallow base also permits the insertion of the driver bit from wider angles, making it an ideal screw for tight spaces.

Phillips II

• The Phillips II, denoted on the head of the screw by a pair of slots, is the next generation of the original Phillips. This second-generation incorporates the exact design specs of the original with the ribs found on ACR Phillips heads. As with the ACR, the Phillips ll eases inserting and removing screws. Additionally, the square corners mean you'll always be able to remove stripped screw heads since you cannot drive a square drive off angle --- an important improvement from the original round corners.

Square Drive

• This head incorporates the cruciform slot formation of the original Phillips with a square drive. Compatible with multiple drive bits, the square drive is ideal for applications that require frequent screw removal. The square drive is also less prone to cam out and capable of higher-torque applications than the original Phillips head.

Tri Wing

• Tamper resistant, the Tri Wing plays a role in both industrial and aerospace industries for high-torque applications. The unique three-slot design can mate only with an ACR Tri Wing driver, making it ideal for publicly accessible screw heads. Each slot has a long, flat side, improving mating and increasing the life of the driver bit due to reduced cam out.