There are many different types and sizes of wrenches, each designed to do a specific job. Therefore, a complete set of wrenches (adjustable, combination ratcheting, etc.) is probably the best buy. Top-quality wrenches are forged from fine-grade tool steel that is hardened and tempered for long service life will cost you a bit more, but they are worth the price. Many better-quality wrenches come with coated grips for ease of handling.
There are too many varieties to list them all, some designed only for a single application, like an oil filter wrench, but the basic types are versatile and belong in most every tool kit.
An open-end wrench provides 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. It has different size openings on each end and should fit the nut exactly to prevent mutilating the nut edges. Some models, called ratcheting wrenches, have ratcheting capabilities. Other varieties, called flare nut wrenches, are flared to fit hex fittings and flare nuts. Generally, these are available in sets.
Box (Box-End) Wrench
A box wrench has an enclosed head and provides 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 inches long and are available with either 6 or 12-point rings. Some models have ratcheting capabilities.
This has a box and an open end on opposite sides of the same wrench. Both ends are usually the same size. A combination wrench is for working on machinery and is the most popular of all fixed-end 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
Commonly called crescent wrenches or C-wrenches, these 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) Wrench
Use a pipe wrench to screw pipes into elbows or other threaded devices. The jaws actually bite into the surface to hold it for turning. They should never be used on plated pipe installations because they will badly mar the finish.
Socket (Hinge Handle) Wrench
The socket wrench combines 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.
The most common type is the detachable socket wrench, with a square drive for hand use. Common square drive sizes are 1/4-inch, 3/8-inch and 1/2-inch, 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.
Also called an Allen wrench, Hex-key wrenches are short, L-shaped tools designed to turn bolts or screws with hexagonal heads. They generally come in sets of different sized wrenches
Ratchet (Socket) Wrench
These are available in a variety of handle shapes and lengths and used with sockets to make turning nuts and bolts easier than with a conventional wrench. Available in 1/4, 3/8 and 1/2-inch drive sizes and are used with socket wrenches.
The round or teardrop-shaped head contains a reversing mechanism to facilitate the tightening or loosening a fastener. Popular accessories include flex handles, speeder handles, T-handles, extensions of various lengths and universal joints to work on fasteners in hard-to-reach locations.
A torque wrench is designed to permit an operator to determine applied torque on bolts, nuts and other fasteners. The torque value (generally measured in foot pounds) is set to a micrometer scale on the handle or preset by an adjusting screw in the handle.
Typically, they have square drives to use standard detachable 3/8 and 3/4-inch sockets. Available with audible signal (clicking sound) or visual display, many torque wrenches are available with dual scales for conventional and metric measurements.
This is another form of pipe wrench, used for tightening and loosening odd-shaped objects, such as pipes and square objects. It has an adjustable chain that wraps around the object, with ends that connect the teeth of the chain to engage and turn the object. Some models feature a locking mechanism with ratcheting action for turning in either direction.
Wrench Safety Tips
Applying excessive torque will strip or damage threads, so quality wrenches are designed to keep leverage and intended load in safe balance.
Users should not put extension handles or “cheaters” on wrench handles to increase leverage. Instead, the proper size wrench should be used.
When possible, a wrench should be pulled, not pushed. Also be sure to brace your stance in case of sudden release or slippage of the fastener.
Never place sockets designed for a hand tool on a power tool or impact wrench.
When breaking loose frozen fasteners, always use a box wrench with a striking face or a heavy-duty socket wrench and a sledge hammer of the appropriate size.
Always make sure the wrench is completely seated on the nut or bolt being fastened—never tilt the wrench at an angle.
When using an adjustable wrench, pull so that the force is on the fixed side of the jaw.
Never use a torque wrench as a conventional wrench.
Courtesy of NRHA.org