What is a socket wrench, and how does it work?

A photo of a 8-24mm socket set.


A socket wrench is a tool used for tightening, or loosening a bolt. It is a wrench, with a given size socket at the end of it. With a regular wrench, you have to physically lift the wrench and readjust it back to your starting position. With a socket wrench, this can be done without lifting the ratchet or socket at all due to a special locking mechanism found in the ratchet head.

Using a socket wrench is quicker, and less troublesome than using a regular wrench.  Ratchets also has the advantage of having a better handle than a wrench, and comes in different lenghts. Length directly correlates to the amount of torque you can apply(Longer = more torque), making it easier to use the correct one for your application.

Price 30$ and up, depending on quality and type.
Recommendation A manual wrench 3/8″ set, with atleast 8-19mm, 6 edged sockets.

Preferrably get 6-24mm, 27,30,32 and 34. One long, and one short socket wrench. Next on the list is a breaker bar, and then an impact gun. Air driven wrench is is also handy, but not needed.

Where to buy Almost any auto shop, or any of the online shops below.
http://biltema.com/ (For European visitors)

How to use a socket wrench

1 – Find, and attach the correct size socket for your bolt or nut.
2 – Flick the switch for either loosening or tightening.
3 – Attach ratchet to bolt, and push/pull. Lefty loosy, right tighty.

You start by finding the correct sized socket for your application. I always start with the smallest one, and move my way upwards. Use a wire brush on dirty or rusted bolts, as the correct size might not fit until you do. Stripping a bolt is very easily done when using the incorrect socket size. Testfit using your hands, before attaching it to the socket wrench.

Using the correct ratchet is also an important step, unless you have only one ratchet. Larger ratchets give more torque, but are harder to use in areas with confined space, while also stripping bolts/threads easier.

Smaller wrenches are recommended when working with smaller bolts(6-13mm), or weaker materials such as plastic, aluminium or magnesium to avoid damage. Smaller wrenches give a more precise feel. The oil sump on an engine, or automatic gearbox are easily damaged by being over tightened.

Showing the difference between a fully seated socket, vs a not seated socket.
Always fully seat your socket before applying force. Not doing so may strip the heads.

Place the socket firmly in place, all the way down on the bolt. Not doing so easily strips the heads. Turning the bolt right will tighten it, and left loosens it. Lefty loosy, righty tighty as the saying goes. 

How NOT to use a socket wrench

The biggest mistake is using the wrong sized socket. I cannot stress this enough. Feel with your hands if the socket seems loose when attached to the bolt, and if it is firmly seated.

Photo showing a 17, and 18mm socket with a 17mm nut inside.
A 17mm nut is used in both sockets. Notice the difference in surface contact.

You might be tempted to use a hammer on the wrench to loosen a bolt. It might work, but it also might ruin your wrench. The same goes for using a pipe to create a cheater bar (Although I often do this myself). The recommended option is getting a larger size.

Type of wrenches – Air driven, impact wrench, manual, breaker bar?

A photo showing all my wrenches
Nearly every wrench in my garage. From left to right – Impact wrench, manual 3/8″, air driven 1/2″ , manual 1/2″,  1/2″ breaker bar.

You have the regular manual socket wrench that uses human force. An air driven version also exists, that with the push of a button automatically tightens, or unwinds your bolt. An impact gun works in the same way. Lastly you have the breaker bar, which is a very long manual wrench for all the torque you need.


This is the one you should get first. Always works, and very easy to use.

+ Can be used anywhere, without the need for electricity or an air compressor.
+ Extremely reliable
+ Very precise in terms of torque applied.
The smallest in size of them all.

 Limited by human strength.
Slower in use than an automatic

Air driven socket wrench

Comes in extremely handy when removing many bolts, such as removing an oil pan that has around 20 bolts that need undoing. However, a manual wrench can do everything that an air driven can.

It does not give a significant increase in torque over a manual wrench , and my air driven wrench(Link to air wrench) outputs 108 Nm at most. In comparison, I have manually tightened flywheel bolts to 125 Nm.

+ Very fast
+ Still somewhat precise amount of torque applied, depending on tool.

Requires an air compressor to function, and therefore electricity.
Cumbersome to drag around as an air hose hangs at the back.
Physically larger than manual socket wrench, and harder to use in tight areas.

Impact wrench/gun

An impact gun has some usage areas that makes the job 10 times easier if you own one. An example of this is removing the lock-nut on a CV-axle. Using a impact gun will shock the nut out, while using a manual wrench will only keep turning the axle around.

My electric impact gun from Biltema gives 450 Nm at most, and cost only 399,- NOK(That is 46 USD).  Electric using a cord or battery, along with air driven versions exist. According to an article on ebay, the corded and air driven are similar, while the battery driven give less torque.  The electric using a cord is the cheapest, and easiest version as it doesn’t require an air compressor.

+ The quickest of them all. Unwind, or tighten a bolt in less than a second.
+ Has an impact function, that loosens most bolts by shocking them over and over.
+ Enormous amounts of torque for unwinding, and tightening.

The large torque amount easily strips bolts and threads.
Not precise at all.
-Requires electricity, or air.
Requires specific sockets. Will destroy regular ones.
Large, and heavy compared to the others. Not suited for areas with confined space.
You may hurt yourself if using the tool wrong.

Breaker bar

I havent met a bolt that survived my breaker bar, literally. The bolt either snaps, or unwinds. They are also cheap to buy, so this is a strongly recommended tool.

+ Extreme amounts of torque applicable.
+ Manual

Very large in size
Strips bolt if not used with caution.

Socket wrench extensions

Showing a bolt reachable by using an extender on the socket wrench.
Removing a bolt from the oil housing assembly on a E36 325 cannot be done without the use of an extender.

Extensions are used when you cannot reach, or firmly place the socket on the bolt. Attaching an extension to your socket wrench solves this problem.

Socket and wrench dimensions

I got my first socket wrench when I was 16, and used it happily for the next two years. Then I got my first car, and required to buy a socket for removing spark plugs.  I walked into the store, and noticed for the first time that sockets and wrenches come in different sizes. 

The size i am referring to is the square connection bolt found at the ratchet head. This comes in 1/4″, 3/8″, and 1/2″. They exist in larger sizes, but they are not used by the hobby mechanic.

A photo showing a 1/2" and 3/8" wrench
The difference between a 1/2″ and 3/8″ wrench socket size

The part of the socket that attaches to your ratchet uses the same sizing system. However, the other end of the socket which attaches to the bolt uses the metric mm, or american inches.

Taller sockets are used to remove items such as sparkplugs, called deep sockets. They slide all the way down to the edges, giving grip where a regular socket cant reach.

Socket pattern

Several types of patterns can be found within a socket. One of them is the regular 6 point, and 12 point used on your regular 6 edged nut and bolt. Other types such as Torx, and Allen patterns exist. Removing the gearbox on a E36 M3 requires Torx, and Allen keys to remove the clutch.

A photo showin all my of my sockets.
All the sockets I have. From top left – Torx, 12 point male, torx male, allen, impact wrench socket, 12 point female, regular 6 point, and a deep impact 6 point socket.
A picture of a 6 point, and 12 point socket.
6 point socket vs 12 point socket. The 6 point is recommended. However, some bolts are actually 12 point and thus require 12 point sockets. The rod bolts in my E36 318is are 12 point.

Tips and tricks

When inserting bolts or nuts they often fall out of the socket on the floor. Counter this problem by sticking a piece of paper inside the socket. The paper tightens the bolt, and makes sure that it stays in place.

Seating sockets on a damaged/rusted bolts can be problematic. Use a hammer with light force to fully seat the socket, to get better grip to avoid stripping the bolt.


– Get a 3/8″ manual wrench and socket set for starters.
– A breaker bar can be extremely handy for those hard to loosen bolts.
– Always make sure that your socket is fully seated.
– Different socket patterns exist. The most used is the regular 6 point.
– Several different square sizes exist for both sockets and wrenches.
– Use an extension where needed.
– Automatic wrenches come in handy.


What do you like/dislike in this article, and is there anything you feel is missing? Please let me know, and I will use it for future articles.

Also, what wrench/sockets do you use the most? I certainly use the 3/8″ socket set the most, as it fits working on my BMW perfectly.

Author: Jehans Jr Storvik

A website with information on how to use tools, and do mechanic work in general with the main focus on cars. This blog is written by a 24 year old computer programmer and amateur mechanic. I have worked on cars since the age of 16, and I learned everything from scratch by myself working on 1990-2000 BMWs. I started with simple operations, and these days I can do engine swaps/rebuilds, suspension overhaul, and building amateur race cars with forced induction. I am a 24 year old computer programmer, and amateur mechanic from Norway. My interest for mechanics started as a child when I disassembled our familys lawnmower to study how it worked. I never got it working again. As I turned 15, I started working on two stroke dirtbikes, and I found the tuning part especially fun. However, a manual 94' BMW E36 325i acquired at the age of 18 turned this interest into a passion. I have since attempted to do all maintenance and mechanical operations myself, to gain further knowledge. These days I am able to do nearly all maintenance by myself, and other things such as: -Engine swaps -Tuning using forced induction, or cam swaps. -Suspension overhauls -Basic welding and cutting. -Basic wire and electric knowledge. -Basic ECU tuning

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