Adjustable wrenches are commonly of the open ended type, and have one movable and one fixed jaw. With and infinitely variable adjustability within their limits, these tools will fit a wide array of bolt and nut sizes, types and thread systems. On the downside, they are bulkier and heavier than fixed wrenches, a fact which is made up for by being able to dispense with a complete set of tools for one.
Just as fixed wrenches do, they are available with heads set at different angles to the handle, with 90 degrees and 15 degrees as the most common. There are several different types to choose from, depending on the application.
Wrought iron slip wrenches, also called wedge spanners or shifting spanners, were among the first of the adjustable wrenches to be developed. They are a simple forerunner to today’s monkey wrench, and although still in use by some, are mostly obsolete.
Several versions of the basic monkey wrench, used to drive nuts and bolts of different sizes, are available. They usually consist of three parts- an integral fixed jaw and handle piece, a movable jaw piece, and an adjusting worm screw.
The adjusting screw is attached to the movable jaw and both parts move along a rack that is integral to the shaft of the handle/fixed jaw. Some variations of the monkey wrench are the back rack wrench, the front rack wrench, the front screw wrench and the center screw wrench.
One of the most omnipresent wrenches in household toolboxes, this steel wrench comes in sizes up to 24 inches in length. It is adjusted via a worm screw captured in the handle which drives against a rack in the moving jaw. One variation has a thumb slider adjustment mechanism placed on its handle for easier adjustment.
Adjustable Box Wrench
This is a double ended box wrench with ends which pivot. The box ends have spring loaded or ratcheted cams in them which automatically close onto the side of the bolt heads of whatever size. As torque force is applied to the wrench, the cam tightens on the bolt for a positive engagement.
Using an Adjustable Wrench
Because the design of an adjustable wrench makes it weaker than a fixed wrench, it is important to use proper technique during their use; otherwise you may damage the nut, injure your hand, or strain the jaws. An adjustable wrench should only be used when use of a fixed wrench is impossible. When removing nuts do not use an overly large wrench or you may end up stripping the threads.
Make sure the nut or bolt head goes as far into the jaws as possible when fitting the adjustment, this will prevent the wrench springing off. Close jaws tightly onto the nut or bolt, while slightly rocking the tool to aid tightening.
An adjustable wrench with its head set angled to the shaft is designed to be used in both directions, so that by turning the tool over you may get a further turn in reduced access areas.
Care and Cleaning
After use, an adjustable wrench should be cleaned with a rag dipped in solvent to remove grease. Maintenance consists of lightly applying oil to the rack and screw from time to time.
Photo by Jo Guldi, Creative Commons Attribution License