Screws and Fasteners - Choosing the Right Driver/Fastener Head
There is often confusion between the many different fastener heads. This guide will help you to pick the head and drive that is right for your job.
Slotted (or REGULAR) Head
Generally large, heavy-duty screws. The tip of the driver is flared so it is wider than the driver bar and can fit more easily into the screw. High quality drivers should be ground for all-around uniformity on the tip. The blade however should not taper too much from the tip because an improper taper can cause it to slip out of the screw slot. The blade of the screwdriver should fit snugly in the slot, and it should be as wide as the head of the screw to prevent it from slipping out of the slot and marring the project. It will also prevent damage to the screw's head and screwdriver tip.
Square Drive (or ROBERSTON) Screws
Square drive screws have increased in popularity in the recent past because of the trend of do-it-yourself deck projects. These drives have a square head to grip the screw better on all four sides and provide better torque and range in size from 0 -3 and jumbo.
Phillips Head Fasteners
Cross-head, or Phillips screw has an X-shaped slot and is driven by a cross-head screwdriver, designed originally in the 1930s for use with mechanical screwing machines, intentionally made so the driver will ride out, or cam out, under strain to prevent over-tightening.
Frearson screw-heads are much like a Phillips head. They also have cross-slots but are V-shaped with tapered sides. Although this screwdriver may fit into many different slots, it is best to use the driver that matches the proper size.
Note: Notice how the Frearson bit (on the left) has a sharp, straight edge, while the Phillips bit (on the right) is rounded.
Socket Set Screws
Socket set screws go in flush! Using an allen wrench, or a hex bit, these fasteners are easy to install. They act similar to machine screws. Hex (hexagonal) tips are commonly used in repairing electronics, especially televisions and radios. They tighten socket set screws and usually come in a set with several different sizes.
Socket Cap Screws
Socket Cap Screws are basically a combination of set screws and machine screws. They can be fastened with either an allen (hex) wrench or an external adjustable wrench, like vise-grips.