What is a universal socket?
A universal socket looks like a standard deep socket but the head is full of small metal pins.
How does a universal socket work?
The pins inside the head of the universal socket are spring-loaded. As the socket is placed over the head of a fastener, the pins in contact with the fastener head are depressed, leaving the remaining pins to surround and grip the fastener head.
This design allows universal sockets to fit many different fastener sizes and head designs, as well as enabling it to turn damaged fastener heads in some cases.
However, the pins inside the socket head do not depress very far, so the universal socket is only able to grip the top of a fastener's head.
What universal socket sizes are available?
Universal sockets come in two sizes: standard and large. The standard size has an overall diameter of 1" (25.4mm) and can be used on fastener heads ranging from ¼" - ¾" (7mm-19mm). It also has a ⅜" drive for connecting a turning tool.
The large size has an overall diameter of 1½" and can be used on fastener heads ranging from 7/16" - 1¼" (12mm -32mm). The drive size of the large universal socket is ½"