Sockets, ratchets and drive tools turn fasteners in assembly, disassembly and maintenance work. The drive size determines the torque range and the access, and using the wrong size is either ineffective or breaks the tool.
Drive size sets the capability. 1/4 in drive is for small fasteners and confined spaces, up to roughly 15 ft-lb. 3/8 in drive is the general-purpose size, covering most automotive and equipment work up to around 80 ft-lb. 1/2 in drive handles heavier work to about 250 ft-lb. 3/4 in and 1 in drive are for heavy equipment and structural bolts.
Socket type follows the fastener. Six-point sockets grip the flats and are less likely to round a fastener; twelve-point sockets engage at more angles and are useful in restricted access, but they bear on the corners and can round a tight fastener. Impact sockets are made from a tougher steel and must be used with impact tools — chrome sockets shatter under impact.
Extensions, universals, adapters and breaker bars extend reach and leverage. Long extensions reduce the usable torque and increase the tendency to twist off; wobble extensions and universals allow access at an angle. Torque wrenches are the tool for anything with a specified torque, and their range must bracket the value being applied.
