The Complete Handbook of Socket Drivers

Chapter 1: Understanding Socket Drivers

A socket driver is a hollow steel tube with a square opening on one end designed to grip the head of a fastener—a bolt, screw, or nut—and transmit rotational force to it. The other end of the socket attaches to a handle, wrench, or power tool. That simplicity masks several layers of detail that determine whether a socket will perform safely, last for years, or fail in the middle of a job.

The most visible difference among socket drivers is size, which comes in two dimensions. The first is drive size: the width and depth of the square male connector that plugs into a handle or ratchet. Common drive sizes are 1/4 inch, 3/8 inch, 1/2 inch, and 3/4 inch. The second is the hex size (or socket size), which is the width of the opening that fits around the fastener head. A 1/4-inch drive socket might have a 5-millimeter hex opening, for example. A 3/8-inch drive socket might open to 10 millimeters. The drive size you choose determines what handles and power tools you can attach the socket to; the hex size determines what fasteners you can grip.

Why this distinction matters becomes clear the moment you try to use the wrong socket. If you use a 1/2-inch drive socket on a 3/8-inch drive handle, it will not fit—the square connector is simply too large. If you use a socket with a hex opening that is too large for your fastener, the