Wrenches and sockets


August 29, 2013 by quirkyuncle

Much of the world is held together with bolts and nuts. If you are going to do any mechanical work beyond the basics, you’ll need to invest in some wrenches and sockets.

While a lot of good work can be accomplished with an adjustable wrench (seen below and described in Essential tools), this tool does have its limits: the head is large and can’t fit into tight places and an adjustable wrench is unable to withstand the torque (turning force) that is sometimes needed to loosen really tight bolts.

Adjustable wrench

A good starter set of wrenches and sockets, as is shown at the beginning of this posting, can be purchased for under $100. It provides a good foundation for performing many maintenance tasks on your car and home. If you require tools beyond what is included in a basic set, they can be purchased one at a time, as needed. This allows you to build your tool collection slowly over time without emptying your wallet. See my posting on Essential tools for information about tool quality and where you can purchase good tools at a reasonable price.

General wrench and socket information
Here are some considerations that apply to both wrenches and sockets:

  • Wrenches or sockets?

    You really need both wrenches and sockets, as each type of tool is better at working under certain conditions. While I tend to use a socket-and-ratchet most of the time, there are instances where a wrench must be used. If I could not afford both types of tool and had to choose one set to start with, it would likely be a set of wrenches, understanding that I would encounter tasks that could not be performed without a socket set. More about the differences between wrenches and sockets is explained below.

  • Metric or English?

    Wrenches and sockets come in sets of standard sizes. Metric sets are sized in millimeters (an ‘mm’ is typically shown on the tool; for example, ’13 mm’). English sets are sized in inches and fractions of inches (no units are typically shown on the tool; for example, a tool for 1/2-inch would be labelled ‘1/2’).

    Most of the world, aside from the USA, uses the metric system. Within the USA, industries are migrating to use of metric hardware. The automotive industry was one of the first to transition to metric fasteners during the 1970s. As a result, most vehicles on the road today use metric hardware.

    If I could only purchase one set of tools, it would probably be metric. I do use my English-inch tools a lot, but in pinch I can usually find a metric tool that fits the English-inch hardware well enough to do the job – not perfect, but close enough.

  • 6-point or 12-point?

    Sockets and closed-end box wrenches can be purchased in 6-point or 12-point styles. The number of points indicates the number of corners that appear in the socket or wrench. In the following photo, a 6-point socket is shown on the left and a 12-point socket is shown on the right.

    6pt and 12pt

    Six point sockets are stronger and will withstand greater torque while having less tendency to foul (round off and render unusable) a bolt head. Sockets and wrenches that are very large, very small, or need to be very strong will be available only as 6-point.

    A 12-point socket offers the convenience of being better able to fit on a bolt that is in a tight location, as it allows you to fit it on the hardware in several ways (the 6-point can only goes on in one way). 12-point wrenches and sockets can also fit onto square-head nuts and bolts (a fastener design that used to be very common), although the size indicated on the wrench used will need to be slightly larger than the actual square-nut size.

  • Bright chrome or matte black finish?

    Most wrenches and sockets have a bright chrome finish. This is a finish of choice for hand tools since it resists corrosion. Some sockets that are finished in a matte black are of a heavier duty for use with pneumatic impact tools (those noisy tools that you hear running in auto repair centers). Impact sockets are built stronger to resist the stresses inflicted on them by an impact wrench – you should never use bright chrome sockets with impact tools, as they can break. (If you want to purchase impact sockets, make sure that they are rated for use with impact tools. Color alone is not a 100% guarantee of tool strength.)

A wrench (called a spanner in the UK) is a tool that grips and turns hardware with flat surfaces, such as nuts or bolts. There are several basic wrench designs suited for use with standard hardware. (There are also many other types of wrenches designed for use with pipes or other types of materials: for simplicity, I’m classifying these other types of wrench as “specialty wrenches” that are not being discussed in this posting.)

  • Open-end wrenches have a U-shaped opening that grips the two opposite faces of a bolt or nut. Open-end wrenches slide onto the fastener from the side, allowing them to be used on plumbing or other fittings where a tube or other protrusion prevents a box wrench or socket from being fit over the end of a fastener. Since open-end wrenches only grip two surfaces of the fastener, there is a limit to the amount of torque you can apply before the wrench slips and fouls the head of the fastener.
    Open end wrench
  • Box wrenches have an enclosed opening that grips all of the faces of a hexagonal-head fastener. (12-point box wrenches can also be used on square-headed fasteners.) Box wrenches, especially 6-point box wrenches, can apply a large amount of torque to a fastener without damaging it.
    Box wrench
  • Combination wrenches have an open-ended wrench on one end and a box wrench on the other end. Combination wrenches are the most versatile wrench design that give the most tool options for the least money.
    Combination wrench
  • Flare wrenches provide five points of contact for a more secure grip on soft fasteners, such as the brass fittings used on flared tubing. Flare wrenches slide onto a fastener, much like a open-end wrench, but can apply additional torque to the fastener without damaging it, much like a box wrench. Flared wrenches are not used often, but can pay for themselves in the time and aggravation you save by not fouling a brass fitting.
    Flare wrench
  • Allen wrenches fit screw or bolt heads with an internal hexagonal hole. There are several variants of the Allen wrench, other than the internal hex, that are in common use, the most prevalent being the Torx head. Allen wrenches are typically available in the L-shaped design (shown below), as a T-handle, or as part of a hex key or multi-driver set (see Essential tools for more information).
    Allen wrench

A word about wrench offset – Wrench heads can be offset from their handle to allow the handle to clear obstructions that might be located near the fastener. Sometimes the additional tool thickness caused by the offset will prevent a wrench from being used in tight locations. If you are purchasing a variety of wrench sets, try to get a mix of offsets so you are prepared for any situation you might encounter.
Wrench offset

A socket is basically a cup shaped box wrenches that attach to a metal handle. This handle then provides the torque needed to turn a bolt or nut. Like wrenches, sockets are available in a variety of sizes and configurations.

  • 3/8-inch and 1/2-inch drive sockets are the most common drive sizes seen in home use. The drive size of a socket refers to the size of the square on the back of a socket that attaches to the metal handle. Larger fasteners require more torque to turn: using a larger drive size allows you to apply a greater level of force.
    3/8-inch and 1/2-inch drive sockets

    Sockets are available in standard depth and deep. Deep sockets allow the tool to be fitted over a nut with a bolt that protrudes from the back that would not allow a standard depth socket to reach the fastener. A variation of the deep socket that contains a rubber insert is used for installing spark plugs. Deep sockets are great, but will not work in all instances due to their greater height. Deep sockets also tend to be weaker. I recommend getting standard depth sockets first and adding the deep sockets later.

  • 1/4-inch drive sockets are also quite common. They are used for small fasteners and typically include a screwdriver handle that allows the sockets to be used as a nut driver.
    1/4-inch drive sockets
  • Ratchets are the most common handle used with sockets. A ratchet applies torque in one direction, while moving freely in the other direction. A mechanism on the ratchet head allow you to choose between torque that loosens or torque that tightens a fastener. Using a ratchet allows you to rotate a fastener quickly when you are unable to make a full 360-degree rotation with the wrench: you apply torque as far as you can rotate the tool, then move the handle in the opposite direction (without spinning the fastener), thereby re-indexing the wrench without removing it from the fastener. Ratchets are available to fit all socket drive sizes (1/4-inch, 3/8-inch, and 1/2-inch drive).
  • Breaker bars (shown at the bottom of the following photo below a ratchet of the same drive size) are long non-ratcheting handles that attach to sockets. Breaker bars are used to apply large amounts of torque to a fastener to ‘break it loose’ or make it very tight – a ratchet could fail in this situation if subjected to too much force.

    A pipe can be slid over a breaker bar in cases where additional extreme torque is required. When using a breaker bar, use the largest drive size possible to avoid breaking the tool, as a larger tool is almost always stronger. Use care when using a breaker bar, since bolts can snap when they are over-torqued. Breaker bars are available to fit all socket drive sizes (1/4-inch, 3/8-inch, and 1/2-inch drive).

    Breaker bar

  • Extension bars allow a ratchet or breaker bar to be moved a distance from the socket, for times when a fastener cannot be reached. Extension bars are available in various lengths – always use the shortest extension bar that you can, as longer extension bars can cause a socket to wobble on a fastener when torque is applied, causing the fastener to foul. Never use an extension bar with a torque wrench, as they render the torque readings inaccurate.
  • Swivel heads allow a socket to be turned by a ratchet or breaker bar when there is no clearance for a normal tool connection. Swivel heads come in several types, such as universal joints, wobble heads, and flexible shafts. All perform a similar function. (See Universal and wobble joints for more information.)

    Swivel heads are not as strong as a normal socket connection, so use care when applying force. They are also very unstable and can easily cause a socket to wobble on a fastener when torque is applied, causing the fastener to foul. Never use any swivel head with a torque wrench, as they render the torque readings inaccurate.

Specialty items
There are many wrench and socket tool variations. This posting covers only basic general-purpose wrenches and sockets that are used in a variety of applications.

Specialty tools are discussed in the DIY postings where they are needed to perform a specific task, such as the oxygen-sensor socket that is described in the DIY – Oxygen Sensor Replacement posting. All specialty tools are listed on the Tools page.

Updated 30 August 2013 – Added link to Tools page.
Updated 6 March 2014 – Added link to Universal and wobble joints topic.


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