Tightening fasteners such as bolts and nuts on vehicles, gun scopes, bikes, home appliances and other applications is a precise science.
They require you to tighten them to the precise torque/extent that the manufacturer intended. If you over-tighten them, you will destroy the threads. If you under-tighten, well, it is a job poorly done.
Please note, torque wrench is only for tightening fasteners and it should never be used to loosen them.
A. Torque wrench definition
This tool applies a specific amount of torque to different fasteners such as lug nuts, lag screws and bolts.
This is different from a regular wrench because it has a special internal mechanism that sets the amount of torque that you can apply on the fastener.
To do this, you would need to know the recommended fastener torque. Usually, it is indicated on the fastener or you can ask the manufacturer.
Since John H. Sharp patented the torque wrench in 1931, this tool has undergone many changes. Today, it is one of the handiest hand tools you can have at home or in an auto garage.
You can adjust the torque settings by hand to meet your needs. You don’t need any other tool to use in combination with this wrench.
B. How to use a torque wrench
This is a fairly simple process, which we are going to demonstrate below:
Find out the torque rating for your fasteners
You need to know the required torque for your fastener. Find out! Check the fasteners themselves or check the user manual for your car or bike.
Adjust the torque application wrench – To change the settings of the wrench, you have to loosen the cap at the end of the wrench in the counterclockwise direction.
It locks the tool setting in place so when you twist it, you loosen the wrench for new settings.
Set the torque
We measure torque in foot-pounds or meter-kilograms. This is why your wrench has big and small numbers on hash marks.
The big numbers are for the meter-kilogram and they are on the body of the wrench. The smaller numbers are for the foot-pounds and they are on the handle of the wrench.
To adjust the settings, just brace the body of the wrench with your left hand, while you use the right hand to turn the dial (clockwise direction to raise torque or anti-clockwise direction to lower it).
Please note that not all torque wrenches twist in either direction. By design, some can slide down or up.
Also, digital torque wrenches have a display screen and keys for entering your torque values.
To get the torque measurement right, lift or twist the handle to a number within 5 foot-pounds. For instance, if you need to tighten a fastener to the torque of 150 foot-pounds, twist the handle to the hash mark that’s between 145 and 155 foot-pound.
Make slight adjustments as required
When you are within range of the torque number that you want to set, move to the dial and then twist the handle ever so slowly to get the exact torque.
If the dial moves independent of the handle, move it slowly in the clockwise or anti-clockwise direction to adjust as needed.
Now, you need to calculate the total torque that you have set to see whether it meets the needs of your fastener.
To do that, check the hash mark and the number it points to on the dial. Add the two numbers (on dial and on the handle) to get the torque in ft-pounds and/or KG-meter.
Lock the tightener
Once you have set the right torque, you have to lock it into place. To do this, brace the torque wrench using your left hand and then twist the tightener in the clockwise direction until it stops moving. You have locked the handle.
To tighten your fasteners
Your wrench is set and the handle is locked in place. Now, place the right socket (depending on your bolt sizes) in the wrench’s head. You can also use an extender if the fasteners you are tightening are in a hard to reach space.
Tighten the fasteners as fast as they can go using your hand, well, unless they are going to a tight place. Once the fastener holds onto the screw, you are ready to tighten with the wrench.
Proceed tightening your fasteners until you hear a click, to let you know when your set torque has been attained.
That is the process of how to use a torque wrench.
C. Units of torque measurement
Torque is measured in Newton-Meters, which is considered as the International Standard of measurement.
This unit is used in the automotive world. The symbols for Newton Meters are N.m/Nm. One N.m is equal to 0.738 pound-feet.
Today, torque wrenches come with two measurements – the imperial and metric systems. It comes with markings and numbers for pound-foot and kilogram-meters.
Sometimes, these measuring units may be expressed in their smaller units. Pounds per foot can be expressed as pounds per inch, and grams per centimeter.
Online, you can find torque conversion calculators, so converting between units need not bother you too much.
D. What is a torque wrench used for?
This tool is used for safe, reliable and precise tightening of different types of fasteners. It helps auto mechanics and other users to know the right amount of force to apply to fasten a bolt, nut or other fastener to the precise torque.
Overall, if you have a piece of equipment that needs precise tightening, this wrench provides that.
You can also use it to tighten scopes on guns. This is where you need precision most if you aim to focus at a point between the eyes of that deer.
You can also use the wrench to tighten fasteners on different parts of your bike. Bicycles, lawn mowers and other things come with fasteners that require precise tightening.
Before you can use this wrench on any bolt, find out whether they have a torque number. If they do not have it, you might want to find out from the user manual. If you set the wrong torque, you can damage your fasteners.
Do not use a torque wrench for loosening fasteners. This tool is only used for tightening but not loosening.
E. Torque wrench dos and don’ts
If you take good care of your tools, they will take good care of you. How should you maintain your torque wrench?
Proper way to store a torque wrench
First, set the wrench at the lowest settings possible and store it to prevent spring damage or failure. Store it and the sockets in the case it came with.
Secondly, it is best to maintain the recommended humidity level around the wrench because metal parts rust easily.
Even with powder coating or choice of stainless and/or other rust-proof material, keep the air moisture content in your storage room low.
It is always good practice to store your tools under room temperature. Before storing your wrenches, you need to clean them, wipe any grease off and check the moving parts for stuck particles.
Proper usage
Something else that can make your torque wrenches sustain damage easily is improper usage.
To reiterate what we have mentioned a few times already, never loosen fasteners with this tool. You should only use it for tightening.
When you are using your wrench, hold it carefully. Do not let it slip off your hand and fall to the floor because that can damage the spring.
Use the wrench for the maximum torque it is made for. Never use extra force to do bigger fasteners than it should work on. Using extensions to overload the wrench is more harmful than useful.
Calibration
Over time, actually, over a few to several uses, torque wrenches start to lose their accuracy. Therefore, you have to calibrate yours often to ensure you are getting accurate readings all the time.
You could take the wrench to a professional for calibration. However, for a handy person, this is something you can do at home.
It will require you to do some math, test and retest the calibration, but it will be worth it. Check the user manual to see how often you should calibrate your torque application wrench. Mostly, these wrenches require calibration once a year or once every 5000 cycles.
Don’t use a torque wrench as a breaker bar
Over time, you will start getting some ideas in your head. One of them is to use a torque wrench as a breaker bar.
A breaker bar applies more torque to bolts to loosen them. Thus, a breaker bar loosens bolts while a torque wrench tightens them.
Therefore, using a wrench as a breaker bar is abusing it. Don’t!
F. Torque wrench parts/Parts of a torque wrench
The parts of a torque wrench are the quick release button, the body (tube), click alarm, handle, two-way dial button, spring, automated lock ring, and lubricating oil.
See the diagram below:
G. Torque wrench accuracy
If you use a torque wrench in any other way apart from what it is intended for, it is going to lose its accuracy and so you will not tighten your bolts and nuts to the right force.
Overall, torque wrenches are never 100 percent accurate, well, unless it is in the laboratory settings. Out here, even wrong storage can affect the accuracy of the wrench.
The accuracy rating of many mechanical and digital torque wrenches is 3 to 5 percent. This is already too inaccurate. You can imagine just how inaccurate the wrench would be if you mishandle it and abuse it.
To maintain high accuracy, you need to calibrate the wrench from time to time. Since this can be an involving process, you can get a professional to calibrate it for you.
When setting the accuracy, use your eyes keenly to read the numbers just right. This is where accuracy starts.
Still on the setting, do not be in a hurry. Mechanical wrenches require precision, so you have to do it so slowly. Turn the dial slowly until you hear the click and then stop immediately.
Use your wrench under the right conditions. For instance, if you are tightening a greasy bolt, the torque setting requirement might be different from that of a dry bolt.
When you have set up the wrench and you are ready to start using it, apply pressure on the handle alone. Avoid applying force on any other part of the wrench as that can affect its accuracy.
H. Torque wrench limitations
It is not all glory for torque wrenches. There is some “doom” too, as you will see here.
It is only good for tightening fasteners
A wrench is only good for tightening fasteners. You cannot use it as a bar breaker because it is not intended for that.
Some sources will tell you that you can use your torque wrench for undoing a bolt, but that is not right. It can affect the accuracy of your tool and it can damage it in other ways.
Using it to tighten anticlockwise threads can be hard
Sometimes, you will have anticlockwise threads and this can be hard, until you get used to it.
Some of your car fasteners and bolts are wound in the anticlockwise direction so to tighten them; you have to use the wrench in the same direction.
You can check the user manual for the wrench to see whether you can use it in the anticlockwise direction. If yes, follow the instructions for that.
It loses its accuracy over time
Torque wrenches require calibration from time to time, because they lose their accuracy. If you store it wrongly, if you drop it, if you overload it, it is going to lose its accuracy.
Even with the proper usage of the torque wrench, it still loses its calibration with frequent usage. If you do not calibrate the wrench, it might not tighten the fasteners accurately.
I. Types of torque wrenches / Torque wrench types
Torque wrenches come in all shapes and sizes. Some are programmable, some are electronic and some are mechanical/manual. Here is a brief overview of the most common types:
i) Manual torque wrench
As the name suggests, manual torque wrenches operate without the need for a power source. They come in different types, so when we refer to manual wrenches, well, it might mean all the wrenches that you can use without connecting them to a power source.
Another way to define these types of torque wrenches is by the way they display the torque reading. The manual ones display it manually, you know, not using any electronic means.
These wrenches are the most affordable to buy. They are also accurate but you have to calibrate them from time to time. With proper usage, storage and calibration, their accuracy is not compromised.
ii) Micrometer torque wrenches
These ones measure torque value in inch-pounds, hence the reason why they are referred to as micro torque wrenches.
Micrometer wrenches give a good option for tightening fasteners in both ways – clockwise and anticlockwise directions.
These wrenches are some of the most vital tools an engine mechanic must have. If you choose one with a narrow head, it can access bolts and nuts even in hard to reach crannies.
iii) Pneumatic torque wrench
This is an advanced torque wrench. It uses an air motor and a torque multiplier mechanism. Even for the heavy tightening jobs, this wrench practically does most of the job, requiring minimal effort from you.
The torque level is controlled by adjusting the air pressure. With the ability to multiply the torque by up to 125 times, these torque wrenches can handle heavy jobs very well.
Another advantage of using a pneumatic torque wrench is that the torque application relies on gears, changing from low to high gear easily.
As a result, there is less vibration. Impact wrenches, which are hammer-driven, have vibration that can get to your hands with long usage.
With torque ranges starting at 118 Nm to more than 45,000 Nm and requiring an air compressor rated for up 20 to 25 CFM, these wrenches are good for medium to heavy-duty works.
iv) Split beam torque wrench
The good thing about this type of wrench is that when the set torque is attained, it will stop tightening the fastener. This eliminates risks of damaging the fastener or the wrench.
This wrench is costlier than a regular beam wrench. You might wonder why you need to buy it. However, it has a higher accuracy rating, sometimes getting to the rate of up to 2% accuracy rate.
You can also measure torque in both the clockwise and anticlockwise direction. If you are looking for a wrench that retains its accuracy over different jobs, this one is just perfect.
V) Digital torque wrench
Digital torque wrenches are popular for their speed, accuracy, precision and even the ability to store memories of various jobs.
Setting it up is far easier and better than setting up a manual torque wrench because you can enter your desired torque range digitally.
You can also choose the torque measurement units that you want from the large array of different systems. The torque is displayed in real-time and better yet, the ratchet head is bi-directional. You can tighten your fasteners in the clockwise and anticlockwise directions.
Vi) Dial torque wrench
These are some of the simplest to use torque wrenches for users of all skill levels. Apart from tightening the fasteners, they also go a few extra miles because (1) They can be used to loosen fasteners safely, without sustaining any damage and (2) They capture the final torque applied on the bolt.
When the set torque is reached, the wrench is going to give you a signal – most of them flash a light and a beep.
That is enough alarm to get you to stop tightening the fastener. There are so many models of the dial torque wrenches, with torque limits falling between 7 in-lbs to 1500 ft-lbs.
vii) Beam torque wrench
This is the most common and most affordable wrench in the market. Walter Percy Chrysler developed it in the 1920s. As the name suggests, a beam torque wrench comes with two beams.
The first beam is a lever for applying the torque to the fastener and the second beam is attached to the head of the wrench. It is the indicator so the free end moves on the scale to show you the torque measure.
When you start tightening a fastener with the beam torque wrench, the lever will be responsible for applying the torque. It is also the handle of the wrench so this is the point where you apply the force.
viii) Flare nut torque wrench
The flare nut type torque wrenches are used on flared nuts. They are used for tightening hexagonal nuts, such as you find on vehicles and plumbing fittings.
Flare nuts need to be tightened to the torque defined by the manufacturer. Only a torque wrench made to use with such nuts can work.
This looks like a regular click torque wrench, but the ratchet head is designed to work with flared nuts. You set the torque using the scale on the handle and when you tighten to the maximum, the ratchet head makes a click sound to alert you that the final torque is attained.
Most of the flare nut wrenches are calibrated to an accuracy range of +/- 4%.
ix) Ratchet torque wrench
This is a type of socket wrench. However, you can use it to loosen a nut without having to remove and reposition it. It does a faster job of loosening fasteners, saving time. Ratchets are different from regular torque wrenches because they are designed to move in a fixed manner and to spin.
When you are tightening a fastener, a fixed ratchet wrench would require you to keep removing it from the bolt to reposition, costing a lot of time.
Because of their flexible nature, these wrenches are best for use in tight spaces. Every DIY enthusiast should have this affordable, easy to use tool.
x) Torque stick
When you have the need to tighten fasteners that do not require precise torquing, you can use a torque stick if you do not have a torque wrench.
However, by design and intention, these sticks are supposed to be used together with an impact wrench. But the torque sticks come with their already preset torque value. Therefore, you just need to know the torque value of the fastener you are using and then choose the torque stick that has the same value.
If you are using the stick type wrench alone, start by tightening the nuts by hand, then when they catch on the threads well, use the stick wrench and tighten to about 70%. For the remaining 30%, use a calibrated torque wrench to finish tightening them up completely.
xi) Electric torque wrench
The electric type of torque wrenches have an electric motor to increase torque. Thus, it does not use impact so it is easy on the hands since there is no vibration.
When you have jobs such as tightening engine head fasteners, they require high precision and that is where you need this type of torque wrench.
Usually, these types of wrenches come with two speed settings, slow and high. These tools work by applying high speed and less torque when the bolt is loose.
Xii) Click torque wrenches
Click type torque wrenches have an accuracy rating of 3 to 5%, which is pretty much within the accuracy range of many other types of wrenches.
It is a manual wrench and it works very well when you learn how to use it. Perhaps this explains why it is the most popular type of wrench in the oil industry.
These tools are also called ratcheting adjustable torque wrenches, and there is a reason for that. You can adjust upward or downward the force you are applying.
The force is indicated by Nm, ft-pounds and inch-pounds. You can set the force you want manually and when the maximum force or bold load has been achieved, there is a lever inside the wrench.
It rolls on a cam, which knocks the inside wall of the handle, making the clicker sound. This is where its name comes from.
xiii) Calibrated torque wrenches
The mechanical and the electric torque wrenches require calibration to maintain their accuracy. If you would rather not deal with all the calibration work, you can take them to a local specialist.
When new, these tools come calibrated for accuracy. Some, such as the torque sticks come with set torque values.
xiv) Type by features
Sometimes, depending on the type of application you wish to put the torque wrench to, you might want to consider more than just the type.
You might want to look at the design of the wrench or the features that it comes with. Here are other considerations that might help you order the best torque wrench type:
Adjustable wrenches – If you can get ½, 3/8, 5/8 or other measurements all rolled into one, you can be able to put that wrench into many uses. Mostly, this is applicable to wrenches that come with ratchet heads, so you can use a different size depending on the job at hand.
Apart from the torque sticks that come with preset torque values, which you might not be able to change, most other wrenches are adjustable.
You can adjust the torque range from, say, 40ft-lbs to 1500ft-lbs and so on. Whether it is a manual or an electric type torque wrench, it should be easy to adjust the force settings.
Flex head torque wrenches – This type of wrench can be used at an angle and still manage to retain its accuracy. Such a wrench is very useful for tightening the fasteners in an engine head.
It can also come in manual or digital mode, with many people preferring the digital one because it is easy to use.
Heavy-duty torque wrenches – For tightening industrial size fasteners, you need to use a heavy-duty tool. This is where the pneumatic torque wrenches come in most handily. They use compressed air for power. They are quiet and practically free of vibrations.
Other torque wrench types to use for heavy duty fasteners are electric types that use a motor and gears. They are accurate, precise and they work fast.
Reversible torque wrenches – This torque wrench type comes with a head design that you can use to tighten fasteners in the clockwise and anticlockwise directions. Left hand fasteners are also called reverse fasteners and they are used in special places where pressure can force right hand fasteners to loosen.
xv) Type by usage
If you want a torque wrench for a specific job, you will find it. Some jobs are more delicate than others and they need wrenches designed just for such. Here are a few:
Torque wrench for scope mounting – Different scope screws require different force. For instance, base screws need a force of 30 inch-pounds while ring cap screws require 16 inch-pounds. This type of work requires the most accurate wrench. Dial torque wrenches are super accurate.
Torque wrench for bike – Most of the bike torque wrenches come with preset torque values of 5 to 6Nm. However, others also come with adjustable torque values. What you buy depends on how often you are going to use it. If you do all of your bike maintenance, get the adjustable ones. If you just need a quick one-off fix, get a couple of fixed torque wrenches.
Torque wrench for lug nuts – You can fix most of the wheel lug nuts with a ½-inch wrench. The torque range should be between 30 and 60 ft-pounds, since most nuts require force within this range. Instead of using a regular wrench or a bar breaker, you can use a torque wrench to tighten the lugs to the right load.
Torque wrench for gunsmithing – In gunsmithing, you always have to repair, adjust parts and fix some of them. You require a set of torque wrenches because guns come with differently sized fasteners. Using regular spanners and screwdrivers can damage your fasteners, or fail to tighten them to the right torque. Get a bi-directional wrench so that you can tighten fasteners in both the clockwise and anticlockwise direction.
Torque wrench for motorcycles – The ¼ and 3/8 inch are the most popular sizes for bike torque wrenches. The torque range for the 3/8 one is between 30 and 60 ft-pounds. Some of the uses for torque wrenches include tightening the spark plugs. The ¼-inch wrench is used for the small fasteners at different places on the body. The torque range is from 4 to 21 ft-pounds.
Some suspension parts of a motorbike might require you to use ½ inch wrench. Thus, it is best to buy a full set of these.
Torque wrench for tight spaces – The choice of a wrench for tight spaces depends on how tight the space is. In some cases, break over torque wrenches are the best. These types of wrenches break or mimic breaking at the pivot point to alert you that the torque value you set is attained.
Torque wrench for spark plugs – Most car spark plugs require a 3/8 inch wrench. They also need to have a load of at least 5 ft-pound.
xvi) Type by material
The type of material used to make the torque wrenches is a big consideration, especially if you intend to use your tools frequently.
Here are some common materials used to make torque wrenches, and their strengths:
ABS Torque wrenches – ABS is high quality plastic material that is used to make vehicle parts, drone parts and other parts that require tensile strength and low weight. You can use such a wrench on carbon fiber bikes.
Aluminum – This is one of the best lightweight materials for torque wrenches. It is strong and rustproof. They require minimal maintenance and care and they can last a long time.
Because of the high quality housing, you get more value for money and a competitive edge if you are running a garage.
Metal – Metal torque wrenches are the most common in the market, with metal handles and housing. If they are not made of stainless steel, they are powder-coated for protection against rust. The only disadvantage with these wrenches is the extra weight, but they are very durable.
Plastic – It is possible to find a cheap plastic wrench. Most of these wrenches are made from single mold acetal plastic. Most of the plastic torque wrenches are used for torquing bike fasteners. You will not find them being used for engine heads, wheel lugs or any other parts that require heavy-duty torque fastening.
Steel torque wrenches –Most of the metal torque wrenches, unless specified as aluminum, are made of stainless steel. These wrenches are common in garages and the oil industry. They can be used for heavy-duty fasteners. The most important thing is to check the torque rating of the wrench.
FAQ: What Is A Torque Wrench?
Finding the right torque wrench for your needs can be hard for the first time. If you still need clarification about what a torque wrench is and how it works, the following questions and their answers can help you:
1. What is the purpose of a torque wrench?
A torque wrench applies the recommended torque to a fastener. These wrenches have adjustable torque values, so you can use them on different fasteners. Just read the manufacturer-recommended torque values for their nuts. These wrenches can also be used to tighten nuts that work in the anticlockwise direction or fasteners in tight spaces.
2. Do you really need a torque wrench?
When you use a bar breaker or a fixed torque wrench, it is easy to break your lug nuts or other fasteners. It is also possible to leave the nuts too loose, in which case you risk losing them. This can also cause serious accidents with equipment, bikes and cars. When you tighten the fasteners to the right torque value, you cannot damage their threads and there is no risk of breaking them.
3. Is it OK to use a torque wrench to loosen?
It is NOT OKAY at all to use a torque wrench for loosening your nuts or other fasteners. This tool is made for tightening fasteners. If you force it to loosen a fastener, it will break, lose its accuracy or damage the nut.
Torque wrenches are high precision tools and using them wrongly even slightly is going to damage the tool and might even make it hard to calibrate in future.
4. What happens if you don’t use a torque wrench?
Many things can happen if you do not use a torque wrench. One of them is damaging the threads of the fastener that you are tightening. This happens when you over-tighten the nuts.
The second one is that you can under-tighten the nuts leaving them loose and the risk of falling off, especially if they are on moving parts. This can cause serious motorbike or car accidents.
Fourthly, you can break the fastener itself or the wrench you are using if you do not use a limited torque wrench. These wrenches are precise, so they help you tighten the fasteners to the extent recommended by manufacturers.
5. Can you tighten with a torque wrench?
You can tighten bike, motorbike, lawnmower, car and farm equipment fasteners using a torque wrench. This does a much better, safer and more accurate job than using a regular wrench or a breaker bar.
You should never use precision torque wrenches to loosen lugs or other fasteners because they are not designed for that.
Final Thoughts for Torque Wrenches
A torque wrench is one of the most important, must-have tools in your toolbox. It is absolutely necessary to have the tool. If you have a bike, motorbike or car, you really need to invest in high quality tools so that you can do the simple maintenance jobs.
To get the full value for your money, you need to know how to use your tools. That is why we have linked out to different articles on how to use various torque application wrenches.