The Wrench
A wrench is a tool specially designed to tighten or loosen nuts, bolts, studs, and pipes. Wrenches are forged from steel alloy to prevent breakage. There are many different types of wrenches. Each type has its own use. By using the proper wrench for the task to be done, you will not break the wrench, damage the equipment, or cause personal injury. The following section is intended to give you information on the different wrench types.
Open-end Wrench
Sold in sets or just one at a time, open-end wrenches are a popular component to any mechanic's tool box. All open-end wrenches have open jaws on one or both ends of the wrench. Most jaw openings are offset from the shank portion of the wrench by 15 degrees.
The wrench length is determined by the size of the jaw opening. The larger the opening, the longer the shaft which helps create the leverage needed to more easily turn the bolt or nut.
Box Wrench
The most efficient of wrenches, a box wrench surrounds the nut, bolt head, or stud on all sides. It is available with both 6-point and 12-point openings. The 12-point opening is more common, as it may be used on both square and hexagonal bolt heads. Box wrench openings are offset from the shank by 15 degrees. A box wrench should be used whenever possible, as it provides the best protection to both the user and the equipment. The major disadvantage of the box wrench is that there must be enough clearance above and around the bolt head to place the wrench over the bolt head.
Combination Wrench
The combination wrench combines the best features of the open-end and box wrench into a single wrench. The size opening on the wrench is the same on both ends, but one end has a box head and the other end has an open-end head. The length of the wrench varies with the size of the head. The most common opening is offset from the shank by 15 degrees. They are used to remove common-size nuts and bolts.
Adjustable Wrenches
Adjustable wrenches come in various sizes. Their advantage is that this one tool has the ability to grab a number of sized nuts and bolts which of course can be a time saver -- especially when you are wedged underneath you vehicle -- no bigger pain than to bring a metric boxed end wrench to a standard job; when you are unsure of the nut or bolt size, the adjustable wrench is a great tool to use.
The adjustable wrenches biggest disadvantage stems from its main advantage, its adjust ability. Because the wrench can be adjusted, it is common to have a little play (no matter how slight) between the wrench's jaws and the nut or bolt you are trying to grasp. This pay can lead to damaging the nut or bolt; commonly, when not careful, it is easy to round off the bolt or nut's edges -- when that happens, you will have a hard time placing a matched sized box end or socket; you may as well replace the bolt or nut.
Torque Wrenches
There are many instances when working on mechanical devices that certain things be in a specific tolerance; for example, the engine's head bolts not only need to be tightened in a specific sequence, they also need to be tightened to the same amount of torque -- to do otherwise is an invitation to oil leaks and a loss of compression. When it comes to ensuring that nuts and bolts are tightened, or not too tight, the torque wrench should be your tool of choice.