A torque wrench is a tool that is used to apply a specific amount of torque to a fastener. This is done in order to prevent damage to the fastener or the object that it is being attached to. There are many different types of torque wrenches, but today experts will be discussing the click-type torque wrench.
This type of wrench has a head that clicks when the desired amount of torque has been reached. This allows you to easily and accurately tighten bolts and screws without over-tightening them. In this blog post, we will discuss how to use a click-type torque wrench!
Advantages of click-type torque wrenches:
- The wrench will not apply more torque than what is set;
- Easy to use;
- Can be calibrated;
- Can be used on any bolt or screw;
- Can be used on any job;
Disadvantages of click-type torque wrenches:
- Not as accurate as a beam-type wrench;
- The wrench will not apply less torque than what is set (so you have to use a different tool for that);
- They can be expensive;
- There is a risk of breaking the wrench if it is over-torqued;
A Brief History of Click-Type Torque Wrenches
The first clicker wrench was developed by Conrad Bahr at the New York City Water Department in 1918, according to tradition. He was irritated that his bolts had inconsistent torque values, so he designed a torque wrench to deliver the same load every time [1].
Bahr wasn’t the first to try to patent the concept. In 1931, John H. Sharp filed a patent for the first torque wrench. The tool he originally called a “torque measuring wrench” is what we now know as a beam-type torque wrench.
To protect against misuse, Bahr also included a mechanism that prevented the wrench from back-ratcheting when the required torque on the fastener was obtained.
How Do Click Torque Wrenches Work?
This is more sophisticated than the socket wrench example. The user can adjust the torque using the clutch mechanism. When the torque level has been achieved, the clutch begins to slip, signifying that a particular torque is required. The click torque wrench is a high-precision mechanism that prevents overreaching and straining of the device until it breaks down. In essence, this is a shut-off function [2].
The wrench has a spring-loaded detent ball that locks the pawl in place when it is engaged. As the user tightens the bolt, the clutch mechanism moves along with it. When the desired torque level is reached, the clutch slips and causes the ball to move out of its locking position.
This releases the pawl and allows it to snap back into place, which creates an audible “click” sound.
This type of torque wrench should not be used for high loads because this may cause permanent damage to both the tool and fastener. It’s mostly designed for smaller applications where there’s no need for more than just a click sound as feedback (instead of the beam or digital wrenches’ visual displays).
Torque Range for Click Torque Wrenches
The minimum and maximum preset torque for clicker wrenches range from 10 to 2,000 ft-lbs. Different torques are available in different gear sizes.
The most common sizes utilized in heavy industrial applications are [3]:
- 3/8-inch square drive size. Torque wrenches are available in a wide range of torque capacities, with typical ratings ranging from 10 to 150 ft-lbs. These are perfect for tight areas where you don’t have enough room on the torque wrench;
- ½-inch square drive size. The most popular are 30-250 ft-lbs torque. These are the most used in the business, and every assembler should have one, or at least access to one. This is also the size of the motor we usually see low profile adapters attached to;
- ¾-inch square drive size. The torque capacity of this ratchet is typically 100-600 ft-lbs. While these can produce a healthy amount of torque on the fastener, they are only 4 feet long, so they may not fit on every application;
Click Torque Wrench Accuracy
The standard ISO 6789 is designed to guarantee consistent torque measurements using hand-operated torque tools, such as general or screwdriver-style torque wrenches.
The normal recommends that calibration be done every 12 months if the tools were used within their permitted limits. If the tool is being used in a company with its own quality control procedures, the calibration schedule can be established according to corporate standards.
Calibration is the comparison of a torque wrench against a known value. This is usually done with either a master torque wrench or an electronic load cell.
Primary calibration checks the accuracy and linearity of the tool over its entire working range. It should be performed by accredited laboratories that use calibrated equipment traceable to national standards.
The marks and numbers on the calibration sheets should all correspond to the manufacturer’s mark, torque range, unit of torque, the direction of operation for unidirectional tools (only allowing you to go in the clockwise direction), and so on.
The precision of clicker wrenches ranges from 3 to 5 percent, depending on the manufacturer. They should be calibrated at least once a year, just like any other tool covered by ISO 6789.
How to Use a Click Torque Wrench:
The Specification
You must first figure out what specification the bolt or screw you’re using needs. This is essential so that you tighten the fastener to the correct degree. You may then use the wrench’s roll dial to select your required torque level. The wrench will have a rolling dial for setting the appropriate torque level and will be marked with a torque rating.
The Fastener
Before using the torque wrench, you should manually thread the bolt or screw by hand. You don’t need to make it very tight. Make sure it is firmly attached to the threads. Attach the socket to the torque wrench right away.
Tightening the Fastener
Make sure that as you tighten the fastener, you keep checking back on it so that it doesn’t get over-tightened (which can lead to damage). When the desired level of tightness has been reached, stop turning! Do not overtighten bolts or screws – this would only lead to a lot of trouble down the road.
There’s also something known as preload. It is common for manufacturers and service manuals to list a preload in ft-lbs (or Nm) for nuts that are being used in conjunction with bearing applications – like wheel bearings or motor mounts – so be aware of this because it can have disastrous consequences if not done correctly!
The Click
A click torque wrench will make clicking sounds when tightening fasteners until they reach their specified level of torque and then stop making noises after reaching that point; this indicates proper operation has been reached while preventing over-tightening issues.
If you go past the click, you will have over-tightened the fastener, which may lead to difficulties. When the pivot point and handle grip reach the breaking force, it is known as a “click”.
A Sequence of Bolts
Occasionally, the two materials must be brought together using more than one bolt. It’s critical to follow the instructions carefully when tightening the bolts. You should double-check the directions. The order in which you tighten the bolts is crucial.
Many times, a criss-cross method is preferable. If you start on a bolt and tighten them in a circular order, you can cause the component to fracture and damage. Consider how long it takes to change a tire on your vehicle. The bolts must be tightened in a criss-cross pattern [4].
Calibration Process of a Click-Torque Wrench
It is suggested that when calibrating a torque wrench, you use the ISO6789 standard, which includes calibration techniques, tool types, and so on.
For calibration, you can use a torque tester or a torque sensor:
- To begin, be sure that the calibration tool is within the proper range. Pre-load the torque wrench with 5 times the maximum torque of the tool;
- Set the wrench with 20% and 60% of the torque range, then take five readings for each setting;
- Then tighten the wrench to 100 percent of its maximum torque range and take 5 readings;
- When you’re checking that all of the readings are within the manufacturer’s endurance range, make sure to double-check each reading for accuracy. If they aren’t, follow the manufacturer’s instructions to adjust the wrench. If required, repeat the procedure; you must achieve torque values in the range;
Safety Measures to Maintain Click Torque Wrench:
- Use the torque wrench in a well-lit area;
- Make sure that there’s no debris or foreign objects on the fastener or socket;
- If you’re using an extension, make sure it is properly calibrated and fits snugly onto the torque wrench and socket;
- Do not use excessive force when tightening bolts; use only what’s necessary to reach the desired torque value. Remember: over-tightening can cause damage;
- When finished with the torque wrench, be sure to clean it and store it in a safe place where it will not be damaged;
- To keep your click torque wrench functioning properly for years to come, take care of it during and after each use;
FAQ
1. How do you read a click-type torque wrench?
When the wrench is set to a certain torque, it will click. Depending on how tight you make the bolt, you may have to go over it multiple times to get it up to the desired torque. After reaching that point, it won’t click anymore and will be at the set torque [5].
2. What type of torque wrench is most accurate?
The dial-type torque wrench is typically regarded as one of the most precise kinds of torque wrenches. The final reading on the dial-type wrench is not affected by the hand-hold position on the wrench, unlike with other types.
Dial-type torque wrenches are wider than some of the others, making them hard to use in confined spaces, and the dial scale must always be visible in order to determine the torque being applied.
They are more costly than standard wrenches, but they are extremely precise. They are also utilized in the aerospace and military industries, in addition to automobile maintenance [6].
3. How many times should you click a torque wrench?
You should tighten the bolt until it clicks the desired number of times as specified by the manufacturer. Do not exceed this amount, as it could damage the component. If you’re unsure how many times to click, always refer to the instructions that came with your torque wrench.
4. How do you adjust a clicker torque wrench?
You must have a torque wrench calibrator or another type of measuring device to adjust your clicker-type wrench. If you’ve lost the instructions for your unit, contact the manufacturer for assistance because each brand is unique and different in how it can be adjusted [7].
Keep in mind that some models do not require calibration! Check with the manufacturer if you’re unsure whether this applies to yours.
5. What does NM mean for a torque wrench?
NM stands for Newton Meters or Newton-meters. It’s the amount of torque applied to a bolt in order to tighten it.
You can convert NM into foot-pounds by multiplying them together (ex: 55 Nm x 0.73 ft/lbs = 40 ft/lbs). If you’re unsure what your torque wrench is set at, always refer back to the instructions for proper use [8].
Useful Video: How To Check and Calibrate Your Torque Wrench
References:
- https://www.hextechnology.com/articles/clicker-wrench-guide
- https://www.doityourself.com/stry/6-types-of-torque-wrenches-explained
- https://www.hextechnology.com/articles/clicker-wrench-guide
- https://www.doityourself.com/stry/how-to-use-a-click-torque-wrench
- https://www.thedrive.com/maintenance-repair/36107/how-to-use-a-torque-wrench
- https://wbtools.com.au/blog/how-to-choose-the-right-torque-wrench
- https://thetorquehub.com/torque-wrench-guide/
- https://www.quora.com/What-is-N-M-meaning-for-torque