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Everything You Need To Know About A Torque Wrench

Everything You Need To Know About A Torque Wrench
14 June 2023 351 view(s)

A tool that is fundamental to mechanics, agriculturists, engineers, technicians, and plumbers is a torque wrench. Furthermore, it may be a tool you need to add to your collection. But why would you need a torque wrench? What does it actually do?

Well, if you would like to start doing your own vehicle maintenance, such as changing your car tyres, then a tool to measure torque is essential.

A torque wrench is invaluable to classic car enthusiasts as it allows them to personally maintain their vehicle and it is vital during rebuilds where certain components will need to be tightened to the manufacturer’s specifications. 

This tool is also a must-have if you are planning to do certain DIY projects within your home where a nut-tightening tool is required.

But how does a torque wrench work? In this blog, we will cover the different types of wrenches there are, such as adjustable torque wrenches and preset torque wrenches, as well as explain what the term ‘torque’ means and how the torque wrench came into existence. 

If you are thinking of acquiring a torque-measuring tool, whether that be for your job or vehicle and home maintenance tasks, then Heamar has a range of torque wrenches to choose from.

What Is A Torque Wrench?
Adjustable torque wrench

They are designed to establish or apply the right amount of torque to a bolt or nut. In simple terms, they enable you to tighten a fastener to its required tension. 

Being able to apply the proper tension helps to ensure that a bolt or nut doesn’t come loose due to under-tightening. Equally, the tool helps to reduce the risk of damage occurring through over-tightening a bolt or nut.

For some machinery, the tightness of its fasteners is crucial to its performance. Additionally, heavy and hazardous machinery, such as mechanical or agricultural machinery, may not be safe to use if any bolts or nuts are not tightened properly, according to the machinery’s requirements. 

The correct level of torque is particularly important in the automotive industry or for those wishing to carry out their own vehicle maintenance tasks. For example, if the lug nuts on a wheel are over-tightened, then it can cause premature brake wear as well as impact the vehicle's ability to stop when the brakes are applied.

Before we go into the history of the torque wrench, we will explain what is meant by the word ‘torque’, so you can understand why the right level of tightness may be vital for any future jobs you wish to undertake.

What Is Torque?

You may have heard the word used often and have some understanding of what it means, but how do mechanics, technicians, and engineers define torque? 

‘Torque’ is the word used to describe a force that causes rotational motion. In simple terms, when you untwist the cap from a bottle, you are applying torque.

The combination of force, which causes an object to accelerate linearly, and torque, which causes an object to accelerate angularly, causes an object to rotate around an axis.

Torque can be measured by lb-ft (pound-feet) or Nm (Newton-metres). Newton metre is a systematic formula for measuring torque, which consists of quantifying the increasing force (Newtons) in proportion to the distance (metres) that is required to rotate (or twist) an object around an axis.

The force that results from one Newton applied perpendicularly to the end of a metre-long arm is equal to one Newton-metre. 

Typically, the symbol for Torque is ‘T’, which is the Greek letter ‘tau’. Torque can also be referred to as the ‘moment of a force’ and the symbol for this is ‘M’.

Richard Salter made the first Newton Metre (also known as a spring scale), but the laws of motion were discovered by Isaac Newton, who was also responsible for the theory of gravity, which is why the Newton Meter was named after him.

However, the concept of torque (also referred to as the ‘moment of a force’), is considered to have appeared in the studies of the ancient Greek mathematician, Archimedes.

Archimedes is known to have said, ‘Give me a lever long enough and a fulcrum on which to place it, and I shall move the world.’

When Was The Torque Wrench Invented?

Now that we have explained what torque is and how the method of measuring torque came into existence, we will delve into the history of the torque wrench.

In 1918, Conrad Bahr invented the first torque wrench whilst working at the New York City water department. This invention enabled consistency amongst the workers when tightening fasteners, reducing the likelihood of leaks and other issues.

However, it wasn’t until 1924, when Walter P. Chrysler invented the flat beam torque wrench, that the genius of the torque wrench spread. Chrysler licensed Paul Sturtevant to manufacture, then, a few years later, was the birth of the Sturtevant Tool Company, which led the way for the torque industry. 

Even though Bahr invented the first torque wrench, John H. Sharp was the first person to file a patent for the tool, which was referred to as a torque-measuring wrench.

Bahr and his partner, George Pfefferle, patented an adjustable ratcheting torque wrench in 1935. 

For a long time, the primary torque wrench was the beam torque wrench. However, over the years, the tool has evolved, undergoing many changes, and now there are many variations of wrenches available.

From dial torque wrenches to clicker torque wrenches, there will be a nut-tightening tool at Heamar to suit your purpose. 

How Do Torque Wrenches Work?
Ratchet and extenion bar being used on car engine

Whilst all torque wrenches work differently, the purpose of each tool is the same. They are designed to apply a specific amount of torque to a nut or bolt. An appliance that has too little torque may not work correctly, whereas if the torque levels are too high, it may cause the appliance to break.

So that an operator knows how much torque is being applied, wrenching tools tend to have a screen or an easy-to-read scale to display the tightness levels of a nut/bolt. Alternatively, there are preset torque wrenches, which allow the torque to be set by an individual and then the tool can be used freely by many people on a manufacturing line.

Within a torque wrench, there is a mechanical indicator connected to an internal calibrated scale. Once the indicator has registered that the desired torque has been met, the operator needs to stop twisting the bolt.

Types Of Torque Wrenches:
Torque wrench ends guide

Below is a range of tools along with the benefits of each to help you discover the best torque wrench for you.

1) Electronic Torque Wrenches
Electronic torque wrench

An electronic torque wrench, which can also be called a digital torque wrench, allows the operator to easily and quickly program a torque value.

Digital torque wrenches, such as the Bahco ⅜” Electric Torque Wrench, have an electronic display, which is where the operator will program the torque levels that are required for the job. 

This type of wrench does not have any moveable parts since it uses an electric sensor to gauge how much twisting force is applied. The electronic strain gauge is generally built within the handle of the tool and, once it has measured the tension, it sends a signal to an LED window. 

Electronic/digital torque wrenches have a small chip inside them where torque readings can be saved, then viewed and assessed on another device, such as a computer. 

They can be the most expensive version of torque wrenches to buy, but the level of accuracy that a digital torque wrench provides is second to none. They deliver a high torque output, requiring little effort from the user. 

Heamar offers a variety of digital torque wrenches, such as the Gedore Torcotronic 120 1/2" Digital Torque Wrench 10Nm - 120Nm. This wrench is ideal to be used during production, quality auditing, research and development (R&D), and maintenance/repair applications. The bi-directional tightening ability of this wrench allows the user to measure torque in clockwise and counterclockwise directions. 

2) Beam

A beam wrench is one of the most basic forms of torque tools. They are generally quite inexpensive and relatively easy to use. 

Beam wrenches have a scale on the handle, which displays the level of torque by a needle that stops when the correct torque is applied. The steel beam deflects as the handle of the wrench is pulled. The reading is taken at the end of the pointer and it is displayed in Newton metres and inch-pounds.

This is a popular wrench amongst mechanics and car enthusiasts because they are very durable; however, it is less sophisticated than a digital torque wrench, although this is to be expected as this type of wrench is more expensive. 

3) Click Torque Wrench
Click torque wrench

This type of wrench delivers an accuracy similar to the beam-style wrench. Additionally, they are simple to use, which makes them a popular choice for many people. 

A click-type torque wrench is so-called because it makes an audible clicking sound to let the user know that the desired torque level has been reached. The clicking sound is caused by the spring-loaded lever as it breaks when the correct torque level is met. The user should listen out for the clicking sound and they should stop tightening as soon as they have heard one click; if they keep on tightening after they have heard the clicking sound, then they are overtightening. 

The majority of click-type wrenches can be used to tighten or loosen nuts and bolts because they are ratcheting. 

Heamar offers the Stahlwille Click-Type Torque Wrench 14mm x 18mm, which does not act on the trigger mechanism after the desired torque level has been met. This means that if a user accidentally applies too much force after the click has happened, it will not cause any damage.

4) Hydraulic Torque Wrenches

A hydraulic torque wrench is lightweight, but it can provide a more accurate and greater amount of torque than other types of wrenches. 

The hydraulic torque wrench was first invented in 1968 by George A Sturdevant. Over the years, this type of wrench has seen many improvements, making it a tool that is often used in industrial environments due to its compact size, accuracy, and minimal effort that is required. 

Furthermore, hydraulic wrenches are designed to prevent over-tightening or over-loosening, preventing the likelihood of damage occurring. 

Hydraulic torque wrenches generate torque using only hydraulic means. Additionally, this type of wrench is self-ratcheting, which means it is very efficient since the user will not have to take out the wrench for every rotation. This efficiency makes them an ideal choice when tightening nuts and bolts in confined spaces.

5)  Dial Torque Wrench
Dial Torque Wrench

Considered to be one of the most accurate wrenching tools, a dial torque wrench is commonly used to test, audit, and verify the torque applied to joints, particularly in automotive and aerospace industries since it is an effective quality control tool.

This type of torque wrench tends to be bigger than others, so it can be harder to use in narrow spaces; however, it does allow for a visual torque verification test to be conducted in a short space of time. 

The Gedore EDS 2000 S 1” Dial Measuring Torque Wrench, which is available at Heamar, is suitable to be used by operators of any skill level. It is easy to use and has a robust design, making it a dependable choice. As well as tightening, this tool can loosen nuts/bolts since it can turn clockwise and anticlockwise if used with the double-ended ratchet. 

6) Slipper Torque Wrench

A slipper torque wrench uses a ‘slipper’ mechanism as opposed to a ‘click’ mechanism. This enables the user to ensure that they are not accidentally overriding the required torque levels, which can be easily done with ‘click’ wrenches. 

The ‘slipper’ mechanism activates once the required torque has been met and, to help you avoid applying too much torque (over-tightening a nut/bolt), the wrench will continue to slip until you have removed it.

Typically a lightweight tool, a slipper wrench is easy to use by anyone of any skill level and allows the operator to work without becoming over fatigued. 

Do Torque Wrenches Need To Be Calibrated?
Ratchet next to an engine

Yes, torque wrenches need to be calibrated so that they can correctly measure how tight or loose a fastener is. Torque calibration is the process of checking the accuracy of the tool and adjusting it, if necessary, so that it meets international standards.

If your wrench isn’t calibrated correctly, then you are highly at risk of over-tightening or under-tightening a nut or bolt, which may affect the performance of your equipment or create a health and safety hazard.

A tool’s reliability and accuracy will diminish over time, particularly if it is frequently used, which means it needs to be calibrated regularly. How frequently a wrench should be calibrated will depend on how often it is used. But the general rule is that a wrenching tool should be calibrated every 5,000 clicks or at least once a year.

Torque wrenches can be calibrated by a professional; however, you can calibrate them yourself by use of torque calibration equipment

A torque sensor measures the torque value of a tool by converting the reading into an electrical signal that can be understood by the operator.

Alternatively, a torque analyser (also known as a torque tester) has a digital screen and is designed to measure and display the output of a wrench. They can also be used to calibrate a wrench so that it can work effectively.

How Much Torque Do You Use On Wheel Nuts?
Torque wrench getting used on car wheel

If you are doing your own car maintenance, then you must apply the correct level of torque to ensure your vehicle is safe to drive.  

For example, if a wheel nut comes loose when driving due to under-tightening, then this can be very dangerous. 

On the other hand, over-tightening wheel nuts (also known as lug nuts) can be just as dangerous since this can damage the wheel. Furthermore, the nut can shear if they are overstretched through over-tightening. 

The optimum torque value is different for every vehicle; however, it is usually between 110Nm and 120Nm.

To find out the torque value for your car, check your vehicle’s manual since it should be stated in there. 

Before you carry out any car maintenance, ensure that you thoroughly understand the vehicle’s requirements as specified by the manufacturer.

Using A Torque Wrench On Spark Plugs
Spark plug

The torque value of spark plugs is very important, playing a major role in whether the engine runs as it should. This is why, when installing spark plugs, the manufacturer’s guidelines must be followed to ensure that the correct torque level amount is applied. Most spark plugs are tightened somewhere between 8 and 40nm (nanometer).

If a spark plug is over-torqued, then it can overheat and it can also cause pre-ignition, where the air and fuel mixture in the cylinder ignites before the spark plug firing.

On the other hand, if a spark plug is under-torqued, it will not be seated properly in the cylinder head, which will cause the dispersion of heat to slow down. Additionally, too much torque can cause the metal shell of the plug to stretch, making it likely the threads will crack or break off.

Whether a spark plug is over-torqued or under-torqued, it can cause severe damage to the vehicle’s engine.

You should avoid tightening spark plugs with your hands as you will not be able to properly ascertain whether they are too tight or too loose. This is why a torque wrench is required. 

Typically, a ½-inch torque wrench is usually sufficient enough to effectively apply torque to spark plugs. It is worth noting that the longer the handle is on a torque wrench, then the more torque can be delivered. 

If you need to remove spark plugs, then only do this once the engine is cool. This is because metal can expand when it is hot, so damage is more likely to occur.

Before you begin installing a spark plug, clean the holes in them to remove any debris since it can affect the level of torque that you apply. 

How To Use A Torque Wrench On Spark Plugs

Are you wanting to change the spark plugs on your vehicle? Read the steps below to find out how to do this safely, reducing the likelihood of causing any damage to your engine.

Ensure that you have the necessary tools. You will need a:

  • Torque wrench
  • Ratchet
  • Spark plugs
  • Gap gauge (a tool that is designed to measure the width of gaps)
  • Brush, cloth, and other cleaning materials 

Clean the ignition oil area. Use a duster or cleaning brush to make sure that no dust or dirt is present in the ignition component. 

Remove the ignition. Do this via the locking tab and remove the connector.

Unplug the screws before taking off the old spark plugs.

Clean the ignition pipe. To do this, use an air compressor. Compressed air will be effective at removing any dust or debris.

If you need to reduce the spark plug gap, use a gap gauge. Read the manufacturer’s guide to find out the correct spark plug gap recommended by the vehicle manufacturer. 

Once the above has been done, you can use your torque wrench. When you are tightening the plugs, apply torque slowly and carefully because the components can easily break.

When you have achieved the correct torque amount, you can connect the wires. Then, screw all of the components back together.

If you cannot find the torque level requirements in the manufacturer’s guidelines, then follow the below steps: 

  • Tighten the spark plug to a finger-tight level
  • Next, for plugs that have a gasket, further tighten, performing another 1/2 of a turn or ¾ of a turn. For plugs that don’t have a gasket, perform another 1/16 of a turn.  

This level of torque is applicable for spark plugs that are 10mm, 12mm, or 14mm in size. 

Spark plugs wear down over time, so if you want to get the most out of your engine, then they need to be changed frequently. Ideally, you should change the spark plugs in your vehicle every 30 months. This will not only help to prevent engine damage but will also help with your fuel economy. 

By replacing old spark plugs with new and more technologically advanced ones, you can improve fuel efficiency by around 1 to 3%. This small improvement will save you money in the long run. 

Torque Wrench Accessories
 Torque wrenh end

Heamar has a variety of torque wrench accessories that are available to order, which can be used with compatible torque wrenches, such as Mountz, Gedore, Bahco, and Stahlwille. 

The accessories include:

How Should A Torque Wrench Be Stored?
Socket set

When you purchase a wrench, it should come in a case. Ideally, this is what you should store your tool in, and you should keep the case in a location that does not have a high or low temperature. 

Furthermore, it should be stored in a dry area that has low humidity. If any condensation is present, it could affect the wrench’s accuracy when measuring torque levels. 

If you are storing your torque wrench for a long period of time (for at least several weeks), then ensure that it is on its lowest setting. Otherwise, if stored at a high setting, it can cause the spring in the tool to weaken. 

However, do not turn the scale to zero. If you fully offload the spring, it may affect the other components, which will have an impact on the tool’s performance and ability to accurately measure torque. 

Before and after every use, ensure that you wipe your wrench with a clean cloth since any dust or grime can damage the tool.

Things To Remember About Torque Wrenches
 Torque wrench and sockets

After reading this article you should understand a lot more about what torque is, why it is important to measure, and how torque wrenches work. 

Here are just a few points to remember when using a torque wrench:

  • Over-tightening a nut/bolt can cause the appliance to break. Alternatively, under-tightening a nut/bolt can cause them to come loose. Both of these instances can be dangerous, causing health and safety hazards.
  • Once you get the signal, which will vary according to the wrench you use, ensure that you stop twisting the fastener. For example, some torque wrenches ‘click’ or ‘slip’ to let the operator know that the torque level has been met.
  • Avoid using a wrench to tighten a nut or bolt fully. You should use a tool like a ratchet to do the initial twisting, then use the torque wrench to ensure it reaches the required torque.
  • Always check the manufacturer guidelines for an appliance to understand the correct level of torque that is required.
  • All tools should be handled and stored with care. A torque wrench is no exception. This type of tool can break easily if not stored correctly. If it is not being used for several weeks, then ensure that it is stored at a low setting; however, do not wind it to zero.

If you are now wondering which torque wrench is best for you and require expert advice, then contact Heamar. We can also assist you with purchasing any compatible accessories to go with your wrench. 

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