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.
Generally, these are large, heavy-duty screws. The tip of the driver is flared so it's 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. However, the blade 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. This will also prevent damage to the screw's head and screwdriver tip.
Square Drive (or Robertson) Screws
Square drive screws have increased in popularity 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. They range in size from 0-3 and jumbo.
Cross-head, or Phillips screw has a cross-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-shaped 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.
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 similarly to machine screws. Hex (hexagonal) tips are commonly used to repair electronics, especially televisions and radios. They tighten socket set screws and usually come in a set that includes 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, such as vise-grips.