Screwdrivers are generally classified as slotted, Phillips head or Robertson (square recess) head, with all three types available with round or square shanks. Quality screwdrivers are judged by the kind of metal in the blade, the finish and amount of grinding on the tip. Material used in the handle, and bar attachment to the handle are other quality indicators.
If blade metal is poor quality, it will chip and crumble under pressure. If the tip is improperly ground and flares too much, it will rise out of the screw slot. If the blade is not attached firmly to the handle, it will eventually loosen and slip in the handle.
Screwdriver Tips
A wide range of screwdriver tips are available: regular, cabinet, Phillips, Frearson, Torx®, clutch-head, hex and square-tipped.
- Regular or slotted tips are used with large, heavy screws. The tip is flared so it is wider than the driver bar. Quality drivers with regular tips should be accurately ground for uniformity. Blades should not taper too sharply from the tip because an improperly tapered tip has a tendency to rise out of the screw slot.
- Cabinet tips are similar to regular tips, but they have no flare. They are straight for use with small screws and countersinking screws where regular tips with a flare would mar the wood or material on the side.
- Phillips head drivers are used on cross-slotted screw heads with modified, U-shaped slots of uniform width. Sizes range from 0 to 4, with 0 being the smallest.
- Frearson screw heads are similar to Phillips. They have cross-slots, but they are V-shaped slots with tapered sides. While a cross-slotted driver will fit many sizes of the type of screw for which it is intended, it is best to use drivers of the proper sizes.
- Torx® drive system provides six lobular drive surfaces mated from lobes of the driving and driven elements. Drive surfaces have vertical sides that permit the maximum torque application to assure reliable clamping force.
- Clutch-head tips have four points of contact. They lock into the screw head when turned counter-clockwise. The driver is unlocked by turning it in the opposite direction. Because of the many contact points, the tip will not damage the screw head.
- Hex (hexagonal) tips are used in repair work in the electronics field, particularly in radio and television repair. They are used to tighten socket set screws and usually come in sets. Some sets are attached to and fold into a metal carrying case. Other variations include T-shaped hex tools with vinyl grips and T-shaped keys for greater torque power.
- Square-tipped (Robertson) screwdrivers have become more common recently because of increased do-it-yourself decking projects. The screwdrivers have a square head and range in sizes from 0 to 3 and jumbo. The square head on the driver helps grip the screw on all four sides to provide maximum torque.
- Multi-bit screwdrivers allow the user to have a number of different types of tips in one tool. Some products keep the interchangeable bits in a self-contained unit.
- Offset screwdrivers are designed for removing and inserting screws in places where it is impossible to use a straight shank screwdriver. They are available in many combinations of slotted and Phillips head tips and with ratchet type mechanisms.
