If you’ve ever seen a mechanic at work in their shop, chances are that you’ve seen a torque wrench in action. These tools look a lot like a socket wrench, but actually do a lot more when it comes to applying precise torque to a bolt or lug.
As a result, torque wrenches are considered a must-have tool for anyone looking to offer mechanic-type services, either as a professional or as an amateur.
But whether you have prior experience in an auto shop or not, you may not fully understand how a torque wrench operates at a mechanical level. This guide will help you understand that process so that you can always ensure that your torque wrench is being utilized properly. This guide will also highlight several different torque wrench types so that you can pick out the type best suited to your bolt tightening needs.
What Is a Torque Wrench?
From the outside, a torque wrench looks like a socket wrench.
In many ways, it shares a similar function to the common socket wrench, but with one important difference. As their name implies, torque wrenches are designed such that they can apply very specific volumes of torque to bolts without exceeding a pre-set limit.
This kind of precise rotational force can be crucial when tightening down car wheel bolts, for example, which can be damaged if they are over or under tightened.
For this reason, a torque wrench is a standard piece of equipment for professional and amateur mechanics. In their most basic form, torque wrenches require just a bit of manual adjustment in order to function properly. However, some newer units have simplified the manual adjustment process with digital components.
Regardless of which type you use, you should understand how your torque wrench works at a basic level before attempting to use it.
How Does a Torque Wrench Work?
A basic torque wrench utilizes a fairly simple operation that even a novice mechanic can understand in a flash. To start, a torque wrench will feature some type of gauge (either analog or digital) that is used to set the desired volume of torque.
A user should do this first, which allows the beams and spring inside the wrench to adjust according to the desired level of rotational force.
Then, a user can lock the socket head onto the target bolt and begin wrenching it down. As this occurs, the main lever inside the wrench will deflect at a predictable angle, thus allowing torque to be applied to the bolt. Meanwhile, a second indicator beam (or a ball, in some cases) moves freely until the desired level of torque is achieved.
At that point, it clicks into place, preventing further torque from being applied to the target bolt.
Beam Torque Wrench
A beam torque wrench is considered the most basic overall in terms of construction, with most units featuring a socket-style head, two parallel beams leading to a grip-able handle, and dial or gauge for setting the torque. These units operate using the basic system described above, with the second indicator beam in this instance attached directly to the torque setting gauge.
However, a beam torque wrench should not be confused with a deflecting beam torque wrench. Those tools are slightly different, particularly in appearance when it comes to their inclusion of a “bent” deflecting beam. These tools do not use an internal spring to detect torque. This job is instead given to the “bent” deflecting beam.
As a result, deflecting beam torque wrenches are more durable and require less frequent calibration.
Click Adjustable Torque Wrench
Though the click adjustable torque wrench is technically a unique type of torque wrench, it is today considered the “standard” type for all intents and purposes. As such, they take on a socket wrench-like appearance and utilize most of the operational mechanics described in the section above in the main “How Does a Torque Wrench Work?” section.
However, they differ slightly when it comes to their internal mechanics.
To be specific, most models use a ball and spring detent internally to apply torque. The spring in question is adjusted in advance such that when a desired level of torque is reached, the ball “clicks” out of place. This prevents further torque from being applied and signals the user to stop with a continued “clicking” noise.
Dial Gauge Torque Wrench
These are a sub-class of a standard beam torque wrench that includes a large, visual dial at the center of its shaft. This dial can be used for even more precise measurements of the torque volume being applied to a particular bolt.
Other than this, they do not typically feature any significant mechanical differences.
Digital Torque Wrench
Digital torque wrenches can utilize either basic beam or click adjustable torque wrench mechanics internally. Regardless of how they apply torque, these wrenches differ when it comes to measuring and communicating said torque readings to the user.
To be specific, these units use an internal strain gauge to determine how much rotational force is being applied to a bolt at a given moment. The on-board computer on these wrenches then converts that strain to a “pound-feet” reading which the user can read reliably.
As a result, digital torque wrenches are often used for quality assurance purposes or any application where the applied torque must be hyper-precise.
How Do Torque Sticks Work?
Also known as “torque limiting extension bars,” these attachments for an impact wrench serve a similar purpose to a torque wrench. These bars are designed to only apply a specific amount of torque, making them easy to implement in a situation where a repeated amount of torque must be applied across many bolts or lugs.
In practice, this occurs when a torque stick is attached to an impact wrench and then connected to the target bolt or lug. Then, when the impact wrench is engaged, the torque stick will rotate and tighten down the bolt or lug as desired.
Once it reaches the torque volume written on the side of that torque stick, this process will cease. Most torque sticks are fairly accurate, though it is always worthwhile to double-check using a standard torque wrench when in doubt.
All in all, there are a number of types of torque wrenches to choose from. While each type functions slightly differently, they are all crucial when it comes to setting lugs and bolts with a precise level of torque.
Be sure to invest in a torque wrench soon, if you don’t already have one. You’ll quickly find that these tools are crucial when it comes to completing numerous automotive maintenance jobs among other things.