How Screwdrivers are Sized
Phillips screwdrivers are sized by manufacturers based on a numerical sizing system, 0 to 24. This is a much different system than the one used for labeling the size of standard flat-line screwdrivers. Flat-line screwdrivers are labeled by their measured sizes, usually inches or millimeters. They are designed to fit a screw of that particular size, and flat-line screw drivers can often fit more than one size screw. Phillips screwdrivers are designed to work with the same length screws, as long as those screws are fitted with Phillips heads.
Phillips Screwdrivers by the Numbers
The number system for Phillips screwdrivers and screws ranges from 0 to 24. This scale runs smallest to largest and refers to the size of the screw. Phillips screwdrivers come in five different sizes, with each size capable of working with at least two sizes of screw. The #2 Phillips screwdriver is the most common, and can fit five different size screws. Phillips #0 fits screw numbers 0 and 1. The #1 Phillips fits screw sizes 2, 3 and 4. Phillips #2 fits screws 5, 6, 7, 8 and 9. Phillips #3 fits the 10, 12, 14 and 16 size screws. The biggest, Phillips #4, fits sizes 18, 20 and 24.
Handle and Shaft length
Any standard screwdriver set will feature both Phillips and flat head screwdrivers in a variety of sizes. Typically, Phillips sizes 0 to 4 are covered, but the length of the handles and shafts can vary. Most sets include a shorter Phillips screwdriver with a 1 1/2-inch shaft. The standard-size shaft for the Phillips screwdrivers found in sets is 4 inches. Some Phillips head screwdrivers feature a shaft that is 8 or 9 inches in length. Some Phillips screwdrivers feature a quick-rotating shaft, which is a shaft with a slight bend in the middle. This bend adds torque when screwing, and allows for a much faster rotation of the screw.
Phillips Head Screw Shapes
Phillips screws also feature a variety of head shapes. Flat, or countersunk, screws have a flat head that is designed to be flush with the wood surface after tightening. Oval head screws, also known as oval countersunk screws, have a head that is similar to countersunk screws except for a rounded top that acts as a more attractive design choice. Round-head screws are designed so that the entire head rests on the surface of the wood. These are the most common type of Phillips screw. Also available are truss, pan, and button-dome screw heads.