A wrench (also known as a spanner outside of North America) is used to grip and help apply torque to rotary fasteners, such as nuts and bolts or to keep them from turning when wrenching down another side. Sized wrenches come in fractions; SAE (Society of Automotive Engineers) and metric. Here is a conversion chart for SAE and metric sizes;
There are over 20 different types of wrenches so here we will just throw out a few basics to get you started;
Commonly referred to as a Crescent wrench, but Crescent is actually a name brand and trademark that made them famous. They come in a variety of lengths and are great tools to have around, one of the first you should purchase. When using them always make sure the adjustable jaw is at the side you are turning, for example; if you are tightening a bolt, the adjustable jaw should be on the left of the nut/bolt, if loosening, it should be on the right, that way the pressure is being put on the “fixed” jaw. The problem with these is they are bulky so you need space around the bolt or nut you are trying to get to.
BOX-END or RING-END
Combination wrenches are the main ones you want to stock up on, long and short types and it seems you can never have too many of either size. You can buy them individually or as a set;
SAE 9 piece set usually consists of; 1/4, 5/16, 3/8, 7/16, 1/2, 9/16, 5/8, 11/16, 3/4
Metric 9 piece (MM) set usually consists of; 7, 8, 10, 11, 12, 13, 14, 17, 19
Another type of these wrenches that are handy to have are the ratcheting box-end type that contain a one-way mechanism which allows the wrench to be turned without removing it from the nut or bolt simply by cycling the handle backward and forward;
The upper one loosens or tightens depending on which side is up. The lower one has a lever where you can easily switch in place the loosening or tightening function.
Next we have the hex key wrenches;
Also commonly referred to as Allen wrenches but Allen is actually a name brand trademark, like Crescent. They are usually shaped as an “L” with hexagon shapes on both ends (some have a ball on one end as shown in the picture, good for swiveling if you can’t get the key in straight) used to drive bolts and screws with a hexagonal socket in the head. They come in metric and SAE as well and are sold usually as a set of each or a set with both types.
Ratchet/socket wrenches are another tool used to torque fasteners (nut/bolt combo) in quicker fashion than a normal wrench. It is a metal handle attached to a ratcheting mechanism normally consisting of a bar or wheel having inclined teeth into which a pawl drops so that motion can be imparted to the wheel or bar.
There are multiple types of square drive head ratchets but the primary use ones are as follows;
1/4″ drive (small) is good for smaller nuts and bolts that you don’t want to over-torque, like electronics. Think of its use as to just snug up nuts/bolts. I recommend using just 1 hand when tightening to prevent over-torque
3/8″ drive (medium) is good for your standard jobs like spark plugs, brake pads, and most under the hood work.
1/2″ drive (large) is more for vehicle lug nuts and larger bolts requiring more torque.
All ratchets allow effective motion in one direction only, but you can switch sides with a locking mechanism located on the back. You can also add things to these for optimal use like;
and swivel extenders
Then you have the sockets that make them function;
Like ratchets, sockets come in three common sizes (drive end) 1/4″, 3/8″, and 1/2″. Like wrenches they come in standard and/or metric sizes. Some can be short (shallow) and others can be tall (deep), some come thick walled for extra torque while others come thin walled for those tight applications. They come in 6 point or 12 point female ends for wrapping around nuts and bolts;
6-point & 12-point
Other accessories you can get to organize or better utilize your socket sets are;
Socket rails to organize those sockets
As well as the speed wrench for quick jobs that require little torque;
Breaker bar for loosening those corroded or over-torqued bolts;
A breaker bar is a long non-ratcheting bar that is used with sockets. Breaker bars are used to break loose very tight fasteners because their additional length allows the same amount of force to generate more torque than a standard length ratchet as well as prevents damage to the ratcheting mechanism of a ratchet. Since it is just used to break, you can switch to a ratchet once you get at least a half of a turn on the fastener.
You can improvise here and just add a long pipe wrapped around the ratchet too, referred to more commonly as the cheater bar
Breaker bars can have 3/8″ or 1/2″ ends but since they are primarily used to remove strong bolts like lug nuts that are applied with great torque by impact wrenches, 1/2″ would be needed the most.
Since power tools can be expensive, this is your best friend when you need to apply heavy torque to break loose or tighten down bolts/nuts.
Torque wrench is used for precise torque power on each nut/bolt.