Wrench Types and Definitions

March 14, 2018

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Wrenches are one tool that more than likely, you will need no introduction to. Wrenches have been around, in one form or another, since the around the 15^th century. Used for leverage, wrenches allow you to turn objects or fasteners and either loosen or tighten them. Available in both standard and metric sizes, today you can still find the basic wrench design, while there are many specialized designs to make certain tasks much easier and more convenient:

Adjustable Wrench: Also known as a crescent wrench, this wrench can be considered sort of a “universal” open end wrench. The adjustable wrench comes with two flat jaws the can be adjusted anywhere from completely closed to completely open and any size in between. On this wrench, the upper jaw is fixed and the opening size is adjusted from a thumb screw near the top of the handle that when turned, will move the lower jaw up or down. These wrenches come in a wide variety of jaw sizes and handle lengths. Some versions also have a box end design, although you don’t see them very often. These wrenches are of great convenience, due to the ability to match the size of any fastener within their jaw limits. The head of the adjustable wrench is larger than most other wrenches, so they don’t necessarily work well in a lot of applications.

Open End Wrench: Exactly what the name implies, open end wrenches can be slide horizontally around a nut or bolt head. This design allows easy access for turning fasteners and also allows the wrench to engage a fastener when a long bolt, tube or threaded rod is in the way since you can slide the wrench onto the fastener from the side. The downside with the open end wrench is that unlike box end wrenches, you don’t have as many points of contact with the fastener, increasing the potential of rounding bolt and fastener heads.

Box End Wrench: The box end wrench gets its name from being completely enclosed. Unlike the open end wrench, this wrench will completely encircle the head of the fastener. This design spreads out the leverage on a larger area, allowing force to be distributed across the entire fastener and resulting in a reduced risk of rounding off the head. Since the box end wrench cannot be engaged from the side, there are certain applications where it cannot be used and you must rely on an open end wrench.

Combination Wrench: The Combination wrench is probably the most popular wrench design available today. Incorporating a combination of both an open end on one side and a box end on the other, this wrench allows the user to simply rotate the wrench to the required design depending on the situation. The combination wrench also eliminates the need to purchase and own multiple sets of wrenches.

Offset Open End Wrench places the open side of the wrench at an angle allowing the wrench to be engaged when objects are in the way and it is not possible to access the fastener from a straight line. These are commonly found in jumbo sizes for suspension work as well as small sizes which are commonly used for ignition systems.

Offset Box End Wrench is designed a little differently than it’s open ended counterpart, usually placing the head that engages the fastener about 1” below the handle, allowing the wrench to easily engage a fastener that is located in a small recess or mounted flush on flat surface.

Flare-nut Wrench: The flare-nut wrench is also known as a line wrench or tube wrench. While the engaging part of these wrenches is open, the opening is only large enough to allow a threaded rod, line or tube to pass through. This allows the faces of the wrench to almost completely engage the fastener greatly reducing the risk of stripping/rounding the head. Commonly used on hydraulic systems, a standard open end wrench can start slipping before reaching the torque required to seal the system.

Obstruction Wrenches: Obstruction wrenches are designed for situations where a standard or offset wrench simply will not work. These include varieties such as “S” wrenches and “half moon” wrenches. Like their names imply, these wrenches are formed into shapes that will allow the head of the wrench to curve around obstacles and engage the fastener. These wrenches can be extremely beneficial in certain situations by eliminating the need to remove components for access to a fastener.

Ratcheting Wrenches: In the never ending quest for time and convenience, ratcheting wrenches have found a place in the toolboxes of most professionals. These wrenches are now available in both open end and box end, as well as with both flexible and offset heads.

Relatively new to the tool market, some open end ratcheting wrenches contain a piston on the open face of the wrench that will compress allowing the head to “slip” across the fastener when ratcheting, while others have a portion of the jaw that moves.

Unlike the open end wrenches, ratcheting box end wrenches have been around for quite some time. The ratcheting box end is almost always a 12 point or spline drive head and is available in both one way and reversible design. The reversible design allows you to change direction of the ratcheting action by flipping a lever while a one way ratcheting wrench design needs to be flipped over to change direction. One benefit of the reversible wrench is it allows you to change direction in the event that an obstacle is in the way and you loosen a fastener to the point where you have no room left to pull the wrench out. If this ever happens with a reversible wrench, you can simply change direction by flipping the lever, re-install the fastener until you have clearance for removal, pull the wrench out and finish the task with and open end wrench.

Socket Wrenches: The “original” ratcheting wrench, socket wrenches have been around for hundreds of years in their non-ratcheting form. The socket, which envelops the head of the fastener, was actually used in the middle ages to wind clocks. This was a most commonly a non-ratcheting square drive version as the ratcheting mechanism was not introduced until the late 1800’s. The square drive socket eventually gave way to the hex head around the 20^th century. Ratcheting socket wrenches rely on a “drive” mechanism which consists of a square drive fitting that usually incorporates a pin detent to hold the socket on. This drive fitting can range in size from ¼” up to 1” for heavy duty applications. The most common drive sizes are ¼”, 3/8” and ½”. A lever on the backside of the head allows you to switch from a tightening to loosening motion. Ratchets come in many varieties of tooth counts these days, with fine teeth ratchets requiring very little swing to engage and rotate. Some ratchets, called “torque wrenches” can be set to disengage when a desired level of torque is reached. However, not all socket wrenches today have ratcheting mechanisms. Lug wrenches and nut drivers are also examples of socket wrenches.

CrowFoot Wrench: Designed for use with a ratchet, and usually coming in open end or flare-nut variety, there is no handle on this wrench. The crowfoot wrench simply has a square hole on the opposite side of the wrench opening, allowing you to operate with a ratchet handle or ratchet extension of the corresponding drive size. These are very useful when access space to a fastener is limited because they minimal space to operate.

Hex Key Wrenches: Simple in design, and often called allen wrenches, hex key wrenches consist of a “key” that fits in a hex-head (six sided hole) of a screw or bolt. These are often shaped like an “L” to give the user increased leverage, but are also available in “T” handle varieties. These can also be found in a socket version which will fit on a ratchet, allowing quicker fastener removal/installation. Other hex key wrenches come with the end portion of the wrench rounded to engage fasteners that can’t be accessed straight on , allowing access even with a degree of offset.

Torx Key Wrenches: Also known as a star-headed wrench, these are designed exactly like the hex key wrenches listed above, only with a 6 pointed star head instead of the hexagon shaped head of the hex key. These are also available in a socket form for use with rachets, however, due to the torx design, there is no variety available for using in offset applications.

Pipe Wrench: Like the name implies, this wrench was designed for using on pipe related applications. The bottom jaw of the wrench is immobile, while the top jaw of the wrench can be raised up or down. This opening/closing action is usually done via a thumb screw near the top of the handle. The upper jaw is a separate piece, with an extension that fits through the thumb screw. Grooves cut in the extension allow the user to open/close the jaw. As the jaws are adjusted just large enough to slide over the pipe, the head will pivot some as the wrench is turned, wedging the jaws and their teeth into place. When used correctly, these can exert a large amount force without slipping, allowing the user to tighten/remove pipes and threaded couplings. These are available in steel and aluminum varieties, the aluminum being much lighter and less fatiguing to use. Due to their design, these will most likely leave teeth marks/gouges on the item you are using them on, so user beware.

Strap Wrench: Just like the pipe wrench above, the strap wrench is designed to turn round items like pipes. These wrenches consist of a strap, usually rubber, which is securely fastened on on end and can slide through a slot on the handle of the wrench. Once you have encircled the item needing to be turned, simply pull the strap tight around the object. As you are turning the wrench, the handle will grab the strap and snug it tight in the direction being turned. While you can’t exert as much force with these as you can with a pipe wrench, this is a great tool to use when you are trying to turn something that you don’t want damaged. I have had great luck with these on plumbing fixtures and seized screw top outdoor lights that are in need of bulb replacements.

Basin Wrench: A basin wrench is wrench most often found in a plumbers tool box. This wrench is specifically designed to remove and install the low profile mounting nuts that secure most faucets. Similar to a crowfoot wrench, only with a handle and spring loaded jaws, the basin wrench gives the user the ability to reach up from under the sink basin and loosen/tighten the nuts holding the faucet to the sink. The head of this wrench pivots to either side depending on whether loosening or tightening is desired.