A wrench's main function is to hold and turn nuts, bolts, caps, screws, plugs and various threaded parts. Applying excessive torque will strip or damage those threads, so quality wrenches are designed to keep leverage and intended load in safe balance. Wrenches can be classified as general use or plumbing wrenches. Top-quality wrenches are forged from finegrade tool steel, machined to close tolerances, hardened and tempered for long service life. Most types are sold individually and in sets of various sizes. Because most imported products are made to metric specifications, a set of metric wrenches has become a must in many home workshops.
Users should not put "cheaters" on wrenches to increase leverage. The proper size wrench should be used. Too large a reach will spread the jaws of an open-end wrench or damage the points of a box or socket wrench. When possible, a wrench should be pulled, not pushed.
- Open-end wrenches provide gripping power on two sides of the head with another side open so the wrench can be placed on a nut, which might not be accessible to a closed or box wrench. Open-end wrenches have different size openings on each end and should fit the nut exactly to prevent mutilating the nut edges.
- Box (box-end) wrenches have enclosed heads and provide more leverage by completely enclosing the nut. Some are offset to provide knuckle room and clearance over obstructions. They range in size from 4" to 16" long and are available with either 6- or 12-point rings.
- Combination wrenches have a box and an open end on opposite sides of the same wrench. Both ends are usually the same size. They are used for working on machinery and are the most popular of all fixedend wrench styles. Also available is a reversible ratcheting combination wrench that allows the user to quickly tighten nuts and bolts without lifting the wrench off and repositioning it after each rotation.
- Adjustable wrenches come in two styles: locking and non-locking. Non-locking styles feature an adjustable end opening with little provision made for slippage. The locking style also has an adjustable–head, but uses a locking mechanism to secure jaws in desired position, eliminating the need for constant readjustment. When properly adjusted to a nut or bolt, it will not slip.
- Pipe (Stillson) wrenches screw pipes into elbows or other threaded devices. Jaws actually bite into the surface to hold it for turning.They should never be used on plated pipe installations because they will badly scar the finish. Aluminum pipe wrenches are popular among professionals because of their lighter weight, but they are more expensive.
- Socket wrenches combine an offset handle with a male drive piece that has a spring loaded bearing to lock on various size sockets. They can be used at almost any angle since handles may be attached to the head by a jointed hinge device. Many socket wrenches have a ratchet handle, making reversing possible in confined spaces.
The most common type is the detachable socket wrench, with square drive for hand use. Common square drive sizes are 1/4", 3/8" and 1/2", and these are normally used in conjunction with a ratchet wrench. Sockets are available with 6-, 8- and 12- point gripping ends, in a full range of inch and metric sizes. A socket wrench combined with a ratchet wrench makes the job of tightening or loosening nuts and bolts faster and easier than conventional wrenches.
- Flare net wrenches are flared to fit hex fittings.
- Hex-key wrenches are short, L-shaped tools designed to turn bolts or screws with hexagonal heads. They also come in sets of different–sized wrenches.
- Ratchet wrenches are available in 1/4", 3/8" and 1/2" drive sizes and are used with socket wrenches. They are available with a round or teardrop-shaped head and contain a reversing mechanism to facilitate tightening or loosening a fastener. Ratchet wrenches are available in a variety of handle shapes and lengths. Accessories that can provide a drive means to socket wrenches include flex handles, speeder handles and T-handles. Extensions of various lengths and universal joints can be used with ratchet wrenches and socket wrenches to work on fasteners in hard to reach
locations. - Locking wrenches are among the most versatile hand tools found in the home or shop. Through a locking action, jaws can be locked in a holding position with pressure up to 1 ton. They can also be used as hand vises, holding clamps, pipe wrenches and hand–vise pliers. They are available with both curved and straight jaws.
- Torque wrenches are designed to permit an operator to determine applied torque on bolts, nuts and other fasteners. They measure torque in ounce-inches, pound-inches and pound-feet, as well as metric measure. However, many manufacturers express torque in foot-pounds (rather than poundfeet) since this nomenclature is more familiar to the average tool user. Two basic hand torque wrenches are audible signal and visual display.
- Metric measure torque wrenches are available in Newton meters (N.m), meter kilograms (mkg) and centimetre kilograms (cmkg) with N.m becoming the more universally accepted calibration. Many torque wrenches are available with dual scales for conventional and metric measurements.
