New Kids on the Block


Phillips and Allen have dominated machine, sheet metal and cap screws for a long time. They are popular, easy to use and easily recognizable. But Phillips and Allen are looking over their shoulders! There are a couple of New Kids on the Block!

The new kids’ names are Torx and Pozidriv. The names may sound foreign but they fit right in the machine screw neighborhood. More surface area and better geometry make these screws more resistant to cam-out — or stripping — as it is more widely known. KNF is still utilizing Phillips and Allen head screws but Torx and Pozidriv are definitely making their presence felt.


Figure #1 (click to enlarge)

Torx are called “star drive” by some, as the recess resembles a 6 pointed star. The six points of contact engagement allows for higher torque being applied than a conventional Allen hex drive of the same size. Torx sizes are denoted by a T, followed by a number from 1 to 100. Common sizes used for KNF products include T6, T10, T15, and T25.

Various Torx screws and drivers are depicted in Figure #1 (left); shown clockwise (from top-left): various Torx screw heads, Torx handles, Torx driver, Torx black & white image.


Figure #2 (click to enlarge)

Pozidriv screws are almost a cousin to Phillips. The Pozidriv (sometimes spelled incorrectly as “Pozidrive”) is actually an improved version of the Phillips screw drive. The name is short for Positive Drive. This screw recess is very easy confused with Phillips if not noticed. Using a Phillips driver for Pozidriv screw recesses can easily result is a stripped head due to the different geometry of the driver itself. The Pozidriv has additional ribs in the driver tip which are received by the secondary web of the Pozidriv screw itself. This extra feature provides more turning strength due to the higher tool engagement. Figure #2 show various Pozidriv screws and drivers; shown clockwise (from top-left): Pozidriv screw heads, Pozidriv handles, Pozidriv driver, black & white image of Pozidriv.

Pozidriv drive bits are designated by the letters “PZ” plus a size code of 0, 1, 2, 3, 4 or 5. Common at KNF are the 0, 1, and 2 sizes. The drivers themselves will have a PZ marking and size code, and possibly the Pozidriv image on the handle butt.

The Pozidriv screws are visually distinguishable from Phillips by a set of radial indents set at 45° from the main cross recess on the head of the screw. These markings are sometime hard to see on plated or treated screws as the treatment may fill in the slighter 45 degree markings.

Please take care to look at these screws carefully before removing for service. Using the right driver will make your servicing quick and efficient. If you are in doubt of which screw is used on your KNF pump, please contact us. We are here for you.


They don’t make things the way the used to, and this can be a good thing, since the latest tools usually incorporate technological advances that improve performance. Please give the “New Kids on the Block” a chance, they are proving to be hard workers!

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