Pozidrive Versus Phillips Screws
by Tony Davis
It is very easy to mistake a Pozidrive screw head for a Phillips screw head. Unfortunately, if the Pozidrive screw is removed with a Phillips the screw head may become damaged. If you have a car with Stromberg carbs, take a look at the 4 Pozidrive screws holding the top cover. If an owner has been using a Phillips driver (yes – it almost fits), the screw heads may be mangled.
The Pozidrive screw heads are marked as shown below with the Phillips on the left and the Pozidrive on the right.
It is very easy to mistake a Pozidrive screw head for a Phillips screw head. Unfortunately, if the Pozidrive screw is removed with a Phillips the screw head may become damaged. If you have a car with Stromberg carbs, take a look at the 4 Pozidrive screws holding the top cover. If an owner has been using a Phillips driver (yes – it almost fits), the screw heads may be mangled.
The Pozidrive screw heads are marked as shown below with the Phillips on the left and the Pozidrive on the right.
One of the differences is in the shape of the slots. The Phillips slots are tapered; whereas, the Pozidrive slots are parallel sided. A Pozidrive screwdriver is less likely to slip in a Posidrive screw. A Phillips driver will not fit a Pozidrive screw correctly.
The Phillips tapers were designed to allow power tools to be used where the driver will cam out of the head rather than twist off the screw head. Viewed from the top the Pozidive head looks like this:
The following description is from www.wikipedia.org.
The Phillips tapers were designed to allow power tools to be used where the driver will cam out of the head rather than twist off the screw head. Viewed from the top the Pozidive head looks like this:
The following description is from www.wikipedia.org.
Screws with the Pozidrive head
The Pozidriv, sometimes purposely misspelled Pozidrive to avoid trademark infringement, screw drive is an improved version of the Phillips screw drive. They can be unscrewed with a regular Phillips screwdriver. It is jointly patented by the Phillips Screw Company and American Screw Company. The name is thought to be a portmanteau of positive drive. Its advantage over Phillips drives is its decreased likelihood to cam out, which allows greater torque to be applied. In ANSI standards it is referred to as type IA. It is very similar to, and essentially compatible with, the Supadriv screw drive.
Phillips drivers have an intentional angle on the flanks and rounded corners so they will cam out of the slot before a power tool will twist off the screw head. The Pozidriv screws and drivers have straight sided flanks.
The Pozidriv screwdriver and screws are also visually distinguishable from Phillips by the second set of radial indentations set 45 degrees from the cross recess. The manufacturing process for Pozidriv screwdrivers is slightly more complex. The Phillips driver has four simple slots cut out of it, whereas in the Pozidriv each slot is the result of two machining processes at right angles. The result of this is that the arms of the cross are parallel-sided with the Pozidriv, and tapered with the Phillips.
This design is intended to decrease the likelihood that the Pozidriv screwdriver will slip out, provide a greater driving surface, and decrease wear. The chief disadvantage of Pozidriv screws is that they are visually quite similar to Phillips, thus many people are unaware of the difference or do not own the correct drivers for them, and use incorrect screwdrivers. This results in difficulty with removing the screw and damage to the recess, rendering any subsequent use of a correct screwdriver unsatisfactory. Phillips screwdrivers will fit in and turn Pozidriv screws, but will cam out if enough torque is applied, potentially damaging the screw head. The drive wings on a Pozidriv screwdriver will not fit a Phillips screw correctly, and are likely to slip or tear out the screw head.
Phillips drivers have an intentional angle on the flanks and rounded corners so they will cam out of the slot before a power tool will twist off the screw head. The Pozidriv screws and drivers have straight sided flanks.
The Pozidriv screwdriver and screws are also visually distinguishable from Phillips by the second set of radial indentations set 45 degrees from the cross recess. The manufacturing process for Pozidriv screwdrivers is slightly more complex. The Phillips driver has four simple slots cut out of it, whereas in the Pozidriv each slot is the result of two machining processes at right angles. The result of this is that the arms of the cross are parallel-sided with the Pozidriv, and tapered with the Phillips.
This design is intended to decrease the likelihood that the Pozidriv screwdriver will slip out, provide a greater driving surface, and decrease wear. The chief disadvantage of Pozidriv screws is that they are visually quite similar to Phillips, thus many people are unaware of the difference or do not own the correct drivers for them, and use incorrect screwdrivers. This results in difficulty with removing the screw and damage to the recess, rendering any subsequent use of a correct screwdriver unsatisfactory. Phillips screwdrivers will fit in and turn Pozidriv screws, but will cam out if enough torque is applied, potentially damaging the screw head. The drive wings on a Pozidriv screwdriver will not fit a Phillips screw correctly, and are likely to slip or tear out the screw head.
