Hydraulic Torque Wrench Use in Industrial Bolting

Hydraulic torque wrenches are a staple in the fastening of industrial bolting applications.

These wrenches are necessary to achieve high torque outputs (greater than 600 ft. lbs.) on a fastener. Manual clicker wrenches capable of reaching 1000 ft. lbs. do exist, but they are brutally difficult to use. Power tools are easier on the assembler and lead to better accuracy and repeatability.

Since hydraulic tools have a high torque output, they need to be powered by a hydraulic pump. This pump or “power pack” relays high-pressure hydraulic force through a hydraulic hose in order to produce the target torque output.

If calibrated correctly, the hydraulic pump will allow the user to change the torque setting accurately. Hydraulic pumps can be powered by either pneumatic (air-driven) or electric power.

Hydraulic torque tools can have a minimum torque of 100 ft. lbs. and a maximum torque of 120,000 ft. lbs.  Both the minimum and maximum torque depend on the capacity and size of the hydraulic equipment. Hydraulic torque wrenches are especially useful on large bolts (1-inch diameter or greater). In the sections below, we’ll explain how hydraulic torque wrenches work, starting with the pumps that power them and working outward to the tools themselves.

Hydraulic Pump (Or “Power Pack”): Where it Begins

A standard pump can generate up to 10,000 PSI, and allow you to adjust the torque setting on the hydraulic wrench. Most pumps work with all major tool brands.

Pumps are either electric or air-driven, though you’ll typically see pneumatic hydraulic pumps used in hydrocarbon processing. Using an electric pump for some bolting applications may require you to get a “Hot Work Permit,” due to the electricity.

For all hydraulic torque wrenches, a hose connects the hydraulic pump to the hydraulic wrench itself. The hose connections (or couplers) are set up so that you cannot hook up the hose incorrectly — the male/female attachments require the right match in order to connect (see photo above). Therefore, connecting the hose to the pump is intuitive and easy.

Hydraulic Hose: Keep an Eye on This Connection


After you power up the pump, you’ll adjust the pressure to match the correlated target torque value on the calibration sheet. The hose attached to the hydraulic tool on what is called the uni-swivel. Logically, the uni-swivel can handle up to 10,000 PSI.

IMPORTANT NOTE: Hydraulic hoses SHALL (i.e. must) be rated for a 4:1 hydraulic pressure, which means rated for 40,000 psi.

There are setting to advance or retract. Advance will fill the piston with hydraulic fluid, which then advances the piston to push on the drive pawls. The drive pawls rotate, which causes the nut to rotate.

ANOTHER IMPORTANT NOTE: Carefully inspect a hydraulic hose for damage or holes before use. If pressurized liquid were to escape through a hole, the stream that would result would be capable of causing severe injury (think: lost fingers or deep cuts).

Square Drive Bolting Tools: Best for Breakouts

The square drive bolting tool is the most common hydraulic torque wrench in industrial bolting. Square drive sizes include ½”, ¾ “, 1″, 1 ½”, 2 ½”. Size dictates the maximum torque output that these tools can generate.

Experience shows square drives are best suited for breaking out, as square drives are more robust and have fewer moving parts than low profile wrenches, making them less prone to breakage.

A square drive tool’s reaction arm places it further away from the flange (due to the impact socket and square drive), therefore square drives are more difficult to use for assembly than a low profile hydraulic torque wrench.

Low Profile Bolting Tools: An Assembler Favorite

Low profile hydraulic wrenches consist of two parts: A powerhead and a link. The link makes low profiles unique because each set of links fit over a specific size of nut. You can change the link by pulling the link pin, then sticking on a differently sized link.

Low profile wrenches go upward from 2,000 ft. lbs. to 4000, 8000, 16,000, and so on. You need a link for every wrench of that size, meaning you might need multiple links for a 2,000 ft. lb. version, multiple links for the 4,000 ft. lb. version, and so on. Links for different model tools are not interchangeable.

As you might guess from the name, Low Profiles are absolutely awesome when dealing with low clearance issues. The reaction point for a low profile is right up against the next adjacent nut. The low-profile wrench may be the assembler’s favorite hydraulic tool because it is easier to use than a square drive.

Hydraulic Torque Wrench Safety

With the high-pressure fluid and extremely powerful mechanical reaction arms, there is great potential for injury with improper hydraulic equipment wrench use. Hex Technology recommends any site that uses hydraulic tools first undergo safe use and operation training.

Always depressurize the hydraulic hose prior to use. Store hydraulic hoses in a circle wrapped end to end, and do not screw the ends on one side together. As mentioned above, if you see any steel braiding bins, cracks, burns or kinks, do not use that hose.

The other major safety concern for all hydraulic torque wrenches is pinch points resulting from reaction points. You know enough physics to know that for every action, there is an equal and opposite reaction. In bolting, this means that if an assembler is applying 1000 ft. lbs. to a bolt, the reaction arm is applying that same amount of force to the adjacent nut. You do not want any part of your body caught between those two pieces of metal.

There are two major types of hydraulic tool designs out there: Those with holding pawls and those without holding pawls. A holding pawl allows the tool to ratchet without using the “wind up” on the fastener. The holding pawl will get bound up on the fastener at some point, and while the tool will ratchet, it will be hard to take off the flange.

When this happens: DO NOT take a hammer to the tool. Instead, power up the tool through the hydraulic pump then depress the holding pawl, and the hydraulic tool will release.

Hydraulic Torque Wrench Maintenance

An important aspect of hydraulic torque wrenches maintenance are watching the seals. Often, these seals are the first thing to break. If you see oil in your hydraulic pump that looks milky, full of water, dirt, or grime, those impurities will travel along with the hydraulic fluid through your tool and eat away at your seals.

The second maintenance factor to mind are the hydraulic hoses. The couplers on hoses regularly get grime and gunk and everything else put through and onto them. Then people will place channel locks or pipe wrenches onto the couplers to try and tighten them. Please clean the fittings with each use so you don’t have to do this, as channel locks will damage and eventually ruin the couplers.

If you have to replace a fitting, please make sure to follow the hydraulic hose manufacturer’s requirements.

The hydraulic pump doesn’t usually require in-field maintenance, but may require some troubleshooting. Air-driven hydraulic pumps will have an FLR, or “filter lubricator regulator.” When you hook up air to your hydraulic pump, there’s a little nozzle on the bottom of the filter. Dump all the water and gunk and grime out before you start running your tool. Because if that gunk and grime go through your FLR, it will travel through the hose into your air motor, and tear up the motor.

You’ll see the FLR has a little sight glass that allows you to see the oil going in. Make sure the oiler is putting in one drip of oil every 10 seconds.  This oil lubricates the air motor, ensuring it doesn’t bind. Having the oil drip more frequently will lead to oil exhaust on the handle, but if the tool doesn’t oil frequently enough, it will bind up the pump and you’ll eventually have to swap the pump out.

It is our recommendation that you reach out to the torque wrench manufacturer. They normally do a safe use and operation and troubleshooting course on their tools, as each different manufacturing and each different model of tool has its own quirks and purposes for each individual part.

After any maintenance on a hydraulic torque wrench, you have to recalibrate the tool. It’s necessary to re-grease both the drive pawls and the side plates so the pawl can move back-and-forth easily against the side plate, doesn’t get bound up, and doesn’t gall.

Calibration: When and what’s required

There are two elements of a hydraulic torque wrench that need to be calibrated:

  1. The actual wrench itself.
  2. The gauge on the hydraulic pump.

Both of these components should be calibrated at least once every 12 months. Once the tool is calibrated, a new torque chart needs to be generated. The updated chart is what your crews will need to use with that tool from that point on. Always check the serial number and date to ensure you have the correct calibration chart for that tool.

If you have questions or your site needs training on the use of hydraulic torque wrenches, contact Hex Technology.

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Bolting Applications with Pistol Grip Torque Wrenches

Roughly 25 years ago, pneumatic torque wrenches (a.k.a. pneumatic torque gun or pistol grip) torque wrenches were commercialized enough to make them one of the main staples for bolting solutions found in oil & gas or power generation.  We have seen the pneumatic torque wrench technology move to both battery and electric powered pistol grip torque wrenches to improve the accuracy and repeatability in bolting applications.  

The oil & gas bolting industry has seen an increase in pistol grip tools as they are ergonomic, heavy duty, have an adequate torque range for most fasteners, and have high-speed continuous rotation without having to ratchet.  This makes them faster than other controlled torque options (such as hydraulic torque wrenches).

We typically see pistol grip wrenches in heavy duty applications because in order to achieve a high torque output (typically greater than 500 to 600 ft-lbs) on a fastener you should where it is easier on the assembler and you can generate better accuracy and repeatability than with an impact wrench or other unregulated “torque tools.”

Pistol Grip torque wrenches consist of a motor (typically powered by air pressure, battery power, or electricity), a gearbox design (planetary gearbox or gearbox) which acts as a torque multiplier,  a square drive, and a standard reaction arm

  • NOTE: These pneumatic tools should not be confused with impact wrenches as impact wrenches do not have an FRL (filter-regulator-lubricator) or another regulated power source (electricity or battery power).
  • Since these pistol grip wrenches have a high torque output typically ranging from 50 ft-lbs to 15,000 ft-lbs. Both the min and max torque range is dependent on the capacity and of the square drive size. Each one of these pistol grip torque tools has a calibration certificate specifically for each tool (serial number and not model) that has the readout of the input vs. the torque value (typically found in ft-lbs or Newton-Meters).  

NOTE: Hex Technology has had significant experience with pistol grip torque wrenches and suggests contacting us if you have further questions after this article.

NOTE: See our articles on Hydraulic Torque Wrenches and Stud Tensioners for other power tool options to achieve high loads on fasteners. 

Pneumatic Pistol Grip Torque Wrenches

The first type of pistol grip torque wrenches that we will discuss is the pneumatic torque wrench. These are powered by air pressure that goes through the air motor, and at the end of the gearbox is a reaction arm that is used to absorb the torque and allows the tool operator to use it with little effort (thus making it ergonomic). These guys are great because they have a very high torque output and they’re normally smaller than an impact wrench as well. 

These advantages include being relatively easy to use. If you’ve used an impact wrench, the only difference with a pneumatic torque wrench is that you’ve got to do is dial your torque with the FRL Some of the best reasons to use pneumatic torque wrenches is they have no vibration, operate at less than 80 decibels, are ergonomic, and they have a higher torque output than what impact wrenches do.  

NOTE: All pneumatic tools are not the same. An impact wrench does not have accuracy or repeatability while pneumatic torque wrenches do. 

Battery-Powered Pistol Grip Torque Wrenches Work

Battery-powered pistol grip tools are more common in the oil & gas industry now than they were 10 years ago, and I project that they’re going to be even more common than pneumatics in the next couple of years because it was just so convenient to use.  

Since they are battery-powered, you do not need an air hose or electrical socket!  They are typically more accurate and repeatable as they have a digital gauge and not a dial gauge.

Electric Powered Pistol Grip Torque Wrenches

The pistol grip wrench that we’re going to talk about is electronic torque wrenches. We don’t see these a lot in the oil & gas industry because it needs electricity, which means you need a hot work permit. We see them more in the power industry, wind industry or structural steel industry, but you can see right here that it’s got an entire box dedicated to setting the torque value and then there’s an output to the wrench itself. Each manufacturer has got strict calibration requirements for these, so please contact them if you’ve got any questions. Do not go into that box and try to adjust it yourself, as that will be a very expensive mistake.

Pistol Grip Torque Wrench Safety

The first thing we’re going to talk about when using these wrenches is safe use and operation. Pinch points are a common safety hazard around the reaction arm of these tools. The reaction arm swings over and reacts against the next nut or possibly the flange. That is not a handle, do not use it as a handle. Keep your hand as far away from the reaction arm as possible. If the torque wrench is putting out a thousand foot-pounds, that reaction force on the reaction arm is going to be a thousand foot-pounds and you’re going to lose a finger.

It is also important that the user have a solid reaction point. Curved or bad reaction points can cause the tool to bind up and put excess load on the gears within the tool. Multiple reaction arms are available from the manufacturer to achieve proper reaction arm placement if the standard reaction arm is not suitable for your application. 

Pistol Grip Torque Wrench Maintenance 

When talking about the maintenance of these tools, you have to remember that they are precision instruments and should be treated that way. Don’t just leave them in the back of the truck overnight. Make sure that they are in an environmentally controlled place so that rain doesn’t get on them, water doesn’t get on them when they’re not in use.

Preventative maintenance will give early detection of worn-out tolerance in these tools and prevent premature failure. For pneumatics, one of the things that we like to do is make sure that when you plug the air in on the FRL, there’s a little nozzle on the filter that you can loosen and it spits out all of the water and all of the dirt that you’ve gotten inside of the hose. Also, make sure that your lubricator is filled with air tool oil. You can see one drip every 10 to 15 seconds from the sight glass of the lubricator.

Unfortunately with the electric and the battery-powered, there’s not a lot of preventative maintenance that you can do on these tools as everything is pretty much closed circuit. The one thing I do not want you to do is go in and try to fix that planetary gear set yourself. It is super complicated with hundreds of moving parts, and you’ll probably end up buying a new tool if you do that. 

Also if you hear anything not working properly, it’s making a grinding noise, don’t keep pulling the trigger because that’s $500 a piece, and get it to a licensed repair shop to get fixed and recalibrated.

Pistol Grip Torque Wrench Calibration Certificate

Calibration certificates for all of the pistol grip wrenches are pretty much the same, and while there is no industry requirement, the standard is to calibrate these once a year. However, these tools should be load verified throughout that calibration year. Meaning you should put them on a Skidmore (or equivalent) and test their accuracy and repeatability just to make sure that the tool is staying within its calibration certificate‘s torque readout.


In conclusion, pistol grip torque wrenches are absolutely awesome to use in the field as they’re super convenient and are high speed (because they do not have to ratchet) compared with other bolting torque methods. With the battery torque wrench, you don’t have to have a hose, you don’t have to have a box, so they’re really easy for the one off flanges. They will probably break down more frequently than the pneumatics just because the handle is not as robust. However, all these wrenches are great for piping flanges, heat exchangers, manhole covers, and any heavy duty bolting applications found in oil & gas

All pistol grips are square drive tools, so If you can fit an impact in there, you can fit one of these torque wrenches in there.

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Bolt Tensioning vs. Torquing: Pros, Cons, and Accuracy

Correct Fastener Preload: What We’re Trying to Achieve

Before we dive into the comparison of bolt tensioning vs. torquing, let’s remind ourselves what we’re trying to achieve when we use either.

The ultimate goal in bolting is to achieve the correct fastener preload (also known as bolt load or axial load). Applied appropriately to a gasketed bolted connection, the bolt load creates clamping force (or “clamp load”) on the gasket. The result: A reliable, leak-free seal.

Bolt torque and bolt tensioning are both legitimate ways to seal a joint. Bolt torquing exerts a rotational force on the fastener, while bolt tensioning involves stretching a fastener with what looks like a hydraulic load cell.

Which is the “best method”?

Well, a torque wrench sales guy would tell you torquing is the way to go. A tensioner sales or service guy would tell you tensioning is the best way to do things. But really, which is “best” is a loaded question, and depends on…

  • Joint criticality
  • Joint component accessibility
  • Available equipment
  • Expertise of personnel

…and more.

In this article, we’ll provide definitions of for bolt torquing and bolt tensioning, explain some pro’s and con’s for each, and offer guidelines for the use of each.

NOTE: For the sake of everyone’s time, we’re not going to talk about tension indicators, hydraulic bolts, or direct tension indicating washers.

What is Bolt Torquing?

A clicker wrench applies torque to a bolt.

Torquing is the most commonly used way to achieve fastener preload with bolted joints. Torquing produces this load through rotational force on a nut or bolt head. This torque is usually measured in foot-pounds (ft-lbs.) or Newton-meters (Nm).

Whether the bolt torque is achieved through the use of a manual “clicker” torque wrench, pistol grip torque wrench, or a hydraulic torque wrench, it is the most simple method of achieving axial load.

The big advantage to torquing is that is typically more cost-effective than tensioning.

However, the skill levels and training of those who use the torque tools equipment are determinants of how successful and accurate torque tightening will be.

Additionally, to achieve correct torque-tension relationship, the K-factor is critical. (And note, K-factor is NOT the same thing as coefficient of friction.) A proper K-factor is critical for understanding what applied torque value you will need.

You also need to take into account friction on bearing surfaces, the bolt diameter, and other variables, which are best examined through experimentation.

What is Bolt Tensioning?

Bolt tensioning on 50% and 25% of bolts within a flange.

As mentioned above, bolt or stud tensioning produces axial load by pulling up on a fastener with what looks like a hydraulic load cell.

To achieve the targeted bolt load, you need to know the area of the tensioner and the amount of force on the fastener, and then adjust the amount of hydraulic pressure.

Hydraulic tensioning began in the 1970s, and in the 50+ years since, tensioning has become more common on specific applications, especially high-pressure flanges with large bolt diameters or critical joints across many industries, including oil and gas, wind, subsea, and power generation.

Because tensioning does not place a twisting force on the fastener as applied torque does, we see tensioners used with long threaded fasteners and on rotating equipment such as reciprocating rods.

Another good use of tensioning is large bolt diameters. On large bolt diameters, tensioning will save you time compared to using hydraulic torque wrenches.

Bolt Torquing vs. Tensioning: What’s More Accurate?

Accuracy of bolt tensioning vs torquing, compared.

Tensioning is more precise — but there are ways torquing can narrow the gap, if it’s applied correctly.

Torque tools are generally considered accurate within plus or minus 30%. That means if your target was 50 KSI of load, you could see anywhere between 35 KSI and 65 KSI bolt load on your fasteners, and you’d be okay with that.

(The differences in bolt load from fastener-to fastener in flange is known as “bolt scatter.” The lower the bolt scatter, the more consistent the flange assembly.)

With tensioning, you’re typically going to see +/- 10% accuracy. That means your bolt scatter will be lower. If the target was 50 KSI, you’d see values between 45-55 KSI.

However, there are some important caveats to note here.

First, tensioning is more expensive and more complicated than torquing. So you will need people who have been properly trained in order to properly apply stud tensioning. Torquing, on the other hand, is fairly simple and torque wrenches are readily available in any industrial plant.

Second, torquing can be significantly more accurate than 30% when performed by an appropriately trained assembler, with proper lubrication and with calculations that include a proper (experimentally determined) K-factor. It’s not uncommon for well-trained craft assemblers to achieve +/- 15% accuracy or better with torquing.


The Stud Guide: B7s, B16s and Other Common Bolts

Torque Calibration in the Lab and the Field

The Myth About Bolt Yield

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The Clicker Wrench Guide: Torque Ranges, Calibration and More

What is a Clicker Wrench?

The Clicker-type torque wrench is the most commonly used torque wrench in the oil and gas industry today.

There’s a good reason why: A clicker wrench is an affordable and extremely accurate tool — so long as you use it properly.

Clicker wrenches are not power tools, but a manual method to achieve proper torque (a.k.a. bolt load) on your fastener. They should be a part of any assembler’s collection of hand tools in every oil and gas plant.

How do Clicker Wrenches Work?

Click Type Torque Wrenches are a ratcheting adjustable torque wrench, meaning you can adjust the applied force up or down within a given range.

Clicker wrenches have a housing that shows such force in either inch-pounds (in-lbs), foot-pounds (ft-lbs) or Newton Meters (Nm), which is used for metric torque settings.

In this article, we’ll concentrate on foot-pounds/Newton Meters, and not micro-clicker torque wrenches (also called micrometer torque wrenches), which measure in inch-pounds because they are typically not used in heavy-duty industrial applications.

The typical click-type torque wrench comes with a manual adjustable setting, but there are also digital torque wrenches available. People may refer to these as electronic torque wrenches. Any of them can help an assembler achieve the desired torque on a fastener.

Most clickers are square-drive torque wrenches. They typically have a ratchet head with drive sizes of 3/8″, 1/2″, or 3/4″. However, most assemblers need to have open-ended attachments for the low clearance issues whey often encounter in the field.

When a clicker wrench is pulled to the point of the torque setting, the lever inside the wrench rolls over a cam and hits the inside of the wrench handle wall. This effect makes the “click” sound, and tells the operator that they have reached the desired torque value.

A Brief History of Clicker-Type Torque Wrenches

It’s generally accepted that the first clicker wrench was created by Conrad Bahr at the New York City Water Department in 1918. He was tired of having inconsistent bolt loads on his fasteners, so he decided to fix it by making a torque wrench that would apply the same load consistently.

(FUN FACT: Torque Wrenches are 100+ years old and most people still don’t know how to use them properly!)

Bahr wasn’t the first to attempt to patent the idea, however. The first patent for a torque wrench was filed by John H. Sharp in 1931. What he then called a “torque measuring wrench” is what we today know as a beam-type torque wrench.

A beam type torque wrench has a torque gauge near the handle.
A beam type torque wrench. (Source: Shutterstock)

But Bahr was not to be left behind. In 1935, Bahr and George Pfefferle patented an adjustable wrench that had ratchet head and that would provide the assembler “audible feedback” — i.e. the “click.”

Bahr also made sure to include a mechanism that prevented the wrench from back-ratcheting when the desired torque on the fastener was achieved.

I would say that Conrad Bahr is a hero in the torque wrench world!

Torque Range for Clicker Wrenches

The preset torque ranges for clicker wrenches range from 10 ft-lbs to 2,000 ft-lbs. Different torques come in different drive sizes. The typical sizes you’ll see in heavy industrial applications are:

  • 3/8″ square drive size: Typical torque range of 10-150 ft-lbs. These are great for areas that you have wrench clearance issues for the length of the torque wrench.
  • 1/2″ square drive size: Typical torque range of 30-250 ft-lbs. These are the most used in the industry and every assembler should have one, or at least have access to one. Also this is the drive size we typically see the low profile adapters used with.
  • 3/4″ square drive size: Typical torque range of 100-600 ft-lbs. While these can produce a good amount of torque on the fastener, they are about 4 feet long, so they might not fit on every application.

Through years of tracking use in the field, Hex Technology has found that 82.3% of applications in the Oil and Gas Industry can be assembled with a click torque wrench that can achieve 250 ft-lbs. That’s nearly the same percentage for the Chemical Industry too.

While manufacturers do make 1,000-foot-pound and 2,000-foot-pound clicker wrenches, they should be treated as a last resort, used only when there is no other option.

Why? Simple: These wrenches are a BEAST on assemblers.

You have to generate 200 to 300 pounds of force on the end of the wrench in order to make achieve your torque. That requires a lot of strength — especially when you consider that they might have to touch 24 studs 4 times if you are using the star method of assembly.

So while a high-torque manual clicker wrench seems like an ok idea in theory, in practice, in order to achieve that level of force, the assembler is either going to have to bounce on the wrench in order to get it to click, or will just become exhausted during the assembly.

Bottom line: If you’re in a situation that requires a 1,000-foot-pound torque wrench or greater, see if you can opt for powered equipment to achieve the torque you are trying to reach.

Clicker Torque Wrench Accuracy, Calibration and Recalibration

Standard ISO 6789 covers the construction and calibration of hand-operated torque tools, including standard torque wrenches and even screwdriver-type torque wrenches.

The standard states that re-calibration for tools used within their specified limits should occur every 12 months. In cases where the tool is in use in an organization which has its own quality control procedures, then the calibration schedule can be arranged according to company standards.

Each calibration sheet should be marked with their torque range, the unit of torque, the direction of operation for unidirectional tools (some tools only allow you to go in the clockwise direction) and the manufacturers mark.

If a calibration/recalibration certificate is provided, the tool must be marked with a serial number that matches the certificate or a calibration laboratory should give the tool a reference number corresponding with the tool’s calibration certificate.

The accuracy of clicker wrenches should be between 3 and 5%, depending upon the manufacturer. And as with any other tool under ISO 6789, they should be calibrated at a minimum of every 12 months.

NOTE: It is common practice — and a very good idea — to also field check the accuracy of these tools between calibration dates.

To do this, you can request a load verifier from the tool manufacturer, place it within your plant, and use it to check that your wrench hasn’t fallen out of calibration.

How to Use a Clicker Wrench

While Clicker Wrenches are accurate, the inaccurate part is the human being. So you’ve got to watch out.

We’ll often combat inaccuracy by putting clicker wrench checkers in the field. Not only does this validate that the wrench is doing what it’s supposed to do, but it also helps to make sure that the human operating the tool is doing what he or she is supposed to do.

Before using a clicker wrench, you want to check that the wrench is set to the desired torque value. When applying force to the wrench, you want to do so evenly — not by jerking, yanking, or jumping on the implement.

Also note: torque wrenches are pretty sensitive. You need to take care when using and handling them. Dropping, hitting, or banging the wrench can change the output of the calibration.

Also, if you don’t completely unwind it to less than 20% of the total scale, you can bend the internal works too much, and they won’t return to their original shape. That will affect your torque value, and may invalidate your calibration.

Other Torque Wrenches You May See

Complexity is the enemy of completion.

Where many people think that technology can compensate for a lack of training or skill, we’ve seen time and again that it doesn’t. Which is why manual click-type torque wrenches remain the go-to tool for the bolting industry.

If you combine this relatively simple tool with a well-trained assembler, you’ll achieve good results.

There are several other types of wrenches available, which we’ll describe below. However please be aware these tools might complicate your procedure process.

Electronic torque wrench

An electronic torque wrench displays a torque value on a digital screen.
An electronic torque wrench displays a torque value on a digital screen. (Source: Shutterstock)

With electronic (indicating) torque wrenches, have a strain gauge attached to the torsion rod, which sends a signal to the transducer and is then converted to a torque value. They typically have a digital display.

Programmable electronic torque/angle wrenches

These are very similar to the electronic torque wrench, but they use a low torque value followed by moving the nut a certain amount of an angle.

The angle measurement is done by a sensor or electronic gyroscope. This design of torque wrench is highly popular with wind power and automotive manufacturers for documenting tightening processes requiring both torque and angle control.

Mechatronic torque wrench

Torque is achieved in the same way as with a click-type torque wrench but it has a digital readout screen (like an electronic torque wrench).

These wrenches also typically have some sort of wireless data transmission with a computer interface so that you can document what torque was applied. We joke that they beep, vibrate, and have flashing lights, so all that’s missing is your old man sitting behind you saying “Stop, stupid!”

There are also manufacturers that are really good at making micrometer torque wrenches like Tekton and GearWrench, but typically we see CDI (a Snapon Company) or Proto Tools in the oil and gas industry for manual wrenches.


Bolt Lubricant and Torque, Explained

The Myth About Bolt Yield

PTFE Coated Studs: Do They Work? 

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Torque Calibration in the Lab and the Field

Why Torque Calibration Matters

The torque wrench is the most-used product for achieving proper load on a fastener. Research shows all torque equipment — manual tools and power tools alike — requires calibration both upon purchase and periodically after use. They will not remain accurate infinitely throughout their lives.

Torque wrench calibration is a critical step in assembly, therefore, because even if you have a great process and skilled labor, your results won’t be good if you don’t have accurate tools.

In fact, the inaccuracies that can result from improperly set torque tools can be huge. We’ve seen in the field that, sometimes, wrenches will “click” at their target of 200 ft-lbs while being off by as much as 50 ft-lbs.

Usually these discrepancies are the result of damage during use. But that damage is often invisible, and therefore undetectable — unless you have some way of testing the tool’s calibration.

In this article, we’ll first review the essential practices of torque calibration. We’ll then discuss common torque tools used in industry, including manual torque wrenches and powered equipment (hydraulic, pneumatic, and battery torque wrenches). Then we will discuss methods for the field verification of these torque tools.

There are some new torque testers that are great for torque applications in the field. We will also discuss the frequency of torque wrench calibration and give you a brief explanation of how it works.

NOTE: The examples of equipment and manufacturers are from our experience only. There might be other options found in the industry.

Torque Tools Calibration: The Basics

All torque tools need to be calibrated by a calibration lab. However, since there is no standard for torque wrench calibration for Powered Equipment, and all torque wrenches experience uneven use, Hex Technology has done research on how to verify your torque wrenches repeatable accuracy while using field testing equipment.

It seems that anyone who performs torque calibration services would verify their calibration lab and methods, but Hex Technology has found that most manufacturers do not verify the calibration process of their employees and distributors. While these companies have NIST traceability on their torque transducers, they often don’t know how the tool actually stalls on the torque application.

It is not hard to do with either a micrometer on a standard fastener (measuring lbf vs. load), force gauges (like a Skidmore) with a fastener, or create their own torque sensor that has been verified. Some manufacturers have done this, but others are behind the curve.

Therefore, while we do not sell these products, Hex Technology recommends verifying your torque calibration service providers with the following methods.

Manual Torque Wrenches

Manual Torque Wrench Calibration Guidelines

Manual torque wrenches or “clicker wrenches” are the most common torque products in the marketplace, the most accurate type of torque wrenches, and have a standard to calibrate to (unlike powered equipment).

The manual torque wrench should not be used when you’re trying to achieve torque over 600 ft-lbs of torque. There are 1000 ft-lb and 2000 ft-lb clicker wrenches are available in the marketplace, but those are beasts for assemblers to use. So please use no greater than 600 ft-lbs.

The accuracy of clicker wrench torque products is between 3 and 5% depending upon the manufacturer. They shall be calibrated every six months per ISO 6789, “Assembly Tools For Screws And Nuts – Hand Torque Tools – Part 2: Requirements For Calibration And Determination Of Measurement Uncertainty.”

Dropping, hitting, or banging the wrench can change the output of the calibration. Also, if you don’t completely unwind it to less than 20% of the total scale after use, the load in the spring mechanism inside the torque wrench will get damaged and your torque wrench will need calibration yet again.

There are many different manufacturers of these wrenches but the ones that we have tested and have worked well are CDI (a Snap-on company), Mountz, and Proto.

Field Calibration for Manual Torque Wrenches (i.e. Clicker Wrenches)

We typically use the NORBAR torque testing equipment (we call them clicker checkers) at the beginning of shifts or use to ensure that the torque wrenches are within +/-5% within their stated torque target. If the wrench does not meet these criteria, you should send it in to your calibration lab for examination. When using these clicker checkers, note that the assembler can have a big effect on its accuracy, so a little training on how to properly use clickers should be a part of this process. We offer free online training for assemblers here. 

Finally, for recalibration, ISO 6789 states that you shall calibrate these tools once a year, regardless of how much (or how little) you may have used them.

Powered Equipment

Electronic torque wrench

The Electronic torque wrench is fairly new to the marketplace. While more expensive than manual torque wrenches, electronic torque wrenches feature a digital display with buttons, so that the predetermined torque value is effortless.

These torque wrenches usually feature ratcheting square drives and many times also include a flexible head. The wrench can make a variety of different indications when the desired torque is met. It can beep and turn colors to alert you. The only thing missing is the old man on your crew sitting behind you saying, “Stop, stupid.

These wrenches have been seen to be more fragile than typical manual torque wrenches. They are also susceptible to the same damage mechanisms (dropping, etc.).

Hydraulic Torque Wrench (low profile and square drive)

Hydraulic Torque Wrench Calibration Guidelines

The hydraulic torque wrench has been around for a long time and was commercialized by Hytorc in 1968. Since then many other manufacturers have emerged, including Torsion X, BoltTech Mannings, and Enerpac.

These torque wrenches can do up to 180,000 ft-lbs and all the way down to 50 ft-lbs. They come in two styles: low-profile and square drive. Most manufacturers claim to have a +/-3% accuracy (of the full scale of the wrench) with 2% repeatability.

When repair services are completed on hydraulics they shall be recalibrated, according to standard, as it will affect accuracy.

Pneumatic Torque Wrench

The pneumatic torque wrench was commercialized by New World Technologies (RAD Torque Tools) 25 years ago and these are gear boxed torque multipliers. These were a step up in speed and ease of use since they weren’t attached to a hydraulic torque wrench pump.

Now there are other manufacturers — Hytorc, Mountz, NORBAR, and many more.

These torque wrenches can produce up to 15,000 ft-lbs and can also go to 50 ft-lbs. They are all square drive tools and claim to have a +/-5% accuracy (of full scale of the wrench) with 2% repeatability.

These are always re-calibrated after repair but you should ensure that they are with your chosen calibration lab.

Battery-Powered Torque Wrench

Pistol Grip Torque Wrench Calibration Guidelines

Our first experience with these was in the early 2000s with RAD Torque Tools in their earlier form. Today, the major manufacturers in the pneumatic marketplace are also making these torque wrenches.

These torque wrenches are becoming far more common in torque application. They are easier to use than pneumatic torque wrenches because they don’t need a basket and air hose to run the motor. Because their use is becoming more widespread, it is critical that the industry understands them better.

These torque wrenches are very sensitive to how stiff the torque application is. Meaning, they perform differently on gasketed torque applications than they do on structural steel torque applications.

They can produce up to 10,000 ft-lbs, but also go down as low as 100 ft-lbs. They are also square drive tools that claim to have +/-5% accuracy (of the full scale of the wrench) with 2% repeatability.

These torque products need to be calibrated after every repair. Thankfully, it’s easy for calibration labs to adjust them.

Calibration for Powered Equipment

Strange but true: There is NO calibration standard in the marketplace for Powered Equipment. Therefore, just because a calibration lab states that they are ISO/IEC 17025 Accredited, it does not mean they know how to calibrate tools correctly. They just follow their procedure. It’s very much like ISO 9000 accreditation. Their torque transducers can simulate either the stiffness of a structural steel joint or a gasketed joint (which is softer). But which are they using?

So we have found that if you want to test a wrench in a lab or shop you can use NORBAR torque sensors which will allow you to verify that your wrench is within +/-10% accurate. This accuracy is acceptable for torque wrench verification.

If you would like to test your tool on an actual torque application, we have used the RAD Smart Socket. This will fit on any size square drive and they make it for different size nuts.

To use the Smart Socket, you just insert your square drive into the socket, turn it on and apply your torque. It will read the torque value and as long as you are +/-10% accurate, you can consider that a win for torque verification.


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