How to Choose Torque Calibrator

Torque Calibrator



Torque Wrenches are one of the most commonly used tools across various industries and sectors.  

The effects of improper torqueing due to defective, worn-out or non-calibrated tools can lead to catastrophic results such as accidents, injuries, and in some cases, death too.

To calibrate torque wrenches, calibration laboratories will have to choose torque calibrators that are accurate. 

Since there are different torque wrench sizes, businesses should consider which torque wrench to buy, what size torque wrench they need and how to select a torque wrench.  

Controlling the torque that needs to be transferred using a torque tool is important for companies to ensure that a product is manufactured within set limits of quality, safety, and reliability. It is also very important to maintain the requirements associated with ISO 9001 quality standard. 

With regular calibration using a torque calibrator, we can ensure that the accuracy of a torque tool is within specified tolerances and maintain continuous quality standards in the assembly process.  

Calibration ensures the performance of a torque tool and indicates the need for such a process. Furthermore, it can identify potential tooling problems such as wear and tear, broken component, etc., before it happens.  

Torque tool calibration equipment has an important role in preventive maintenance along with traceability to assure all measuring results are in accordance with national/international standards. 

Check out the white paper on difference between ISO 6789:2003 and ISO 6789:2017 

There are many types of torque wrenches. Major categories are listed & explained below –  

Type 1 type Torque tools (Indicating Type) 

Indicating type tools indicate by means of a mechanical scale, dial or electronic display, showing the amount of torque exerted by the tool at the output drive.  

Type I Torque tools are further classified as follows: 

  • Class A: Wrench, torsion or flexion bar (coil spring or deflecting beam torque wrench) 
  • Class B: Wrench, rigid housing, with scale or dial display 
  • Class C: Wrench, rigid housing and electronic measurement 
  • Class D: Screwdriver, with scale or dial display 
  • Class E: Screwdriver, with electronic measurement 

Type 2 type Torque tools (Setting Type)  

Torque tools of this category is pre-set type, whereas a certain torque value needs to be preset, so that, when the desired torque value is exerted by the tool at the output drive, an audible or visible signal is released.  

Type II Torque tools are classified as follows: 

  • Class A: Wrench, adjustable, graduated or with display 
  • Class B: Wrench, fixed adjustment 
  • Class C: Wrench, adjustable, non-graduated 
  • Class D: Screwdriver, adjustable, graduated or with display 
  • Class E: Screwdriver, fixed adjustment 
  • Class F: Screwdriver, adjustable, non-graduated 
  • Class G: Wrench, flexion bar, adjustable, graduated (adjustable beam type torque wrench with graduated scale) 

Torque tools need to be calibrated using a torque calibrator regularly as their repeated usage causes them to lose their accuracy and setting points. Their calibration integrity depends upon the usage and environment to which the tool is subjected.  

According to ISO 6789-1:2017 guidelines  

Torque tools must be calibrated after every 5,000 cycles or Twelve months, whichever is earlier. If any tool is found to be out of calibration, it must be recalibrated, retested, and recertified. To ensure that such a slip does not happen again by oversight, the calibration interval for that particular tool is then cut down to 2,500 cycles or six months. 

How to Select a Torque Calibrator?  

Torque Tool Calibration System 

To calibrate torque wrenches, calibration laboratories will have to choose Torque calibrators that are accurate. These systems are quality control devices used to calibrate torque tools. The systems can operate both in clockwise and counter-clockwise directions. These can also convert the reading into several torque units. And they have three modes of operation, namely peak, first peak, and track.  

Torque tool calibrators comprise of the following parts –  

Torque Transducer 

A torque sensor is a device that measures and records the torque on a rotating system. Torque sensors are transducers that convert mechanical torque input into an electrical output signal. There are two types of torque sensors. Strain gauge based and reaction type torque transducers that can be used along with a torque tool calibrator. 

Digital display Unit:  


A digital display is used to measure the output signal from the torque transducer. This is then used to calculate the value of the torque which is displayed on the screen 

Joint Simulator 

The joint simulator is used during the calibration process to help test torque tools. The joint simulator is placed on top of the transducer. By using different types of springs, the joint simulator can have soft, medium or hard joints. 

Calibration Software:  

The PC Software in the upgrade pack helps the user print calibration reports after all uncertainty calculations. It also has an audit mode to verify the uncertainty calculations. 

Product Selection Guidelines: 

  1. Decide on the ISO Standard for which you should calibrate your tools (Ex: ISO 6789:2003 / ISO 6789: 2017) 
  1. Decide on Type of Torque Tools to be Calibrated (Type, Size, Capacity etc.,) 
  1. Decide Min and Max Torque Tool Capacities to be Calibrated 
  1. Select Max Capacity of the Test Rig as per max torque tool to be calibrated 
  1. Select the Control option for which your system to be operated – Manual/Automated/Computer Controlled? 
  1. Choose the appropriate torque transducer with Required accuracy & required capacities  
  1. Opt for software package for automated uncertainty calculation & automated calibration reports. 


Sushma’s solution for calibration of static torque tools as per ISO 6789:2017-2 is the Torque Wrench Calibration System. Our latest product is designed to ensure that you have the best appliance while complying with the new complex ISO standard.  

We offer two models – Automated and Computer Automated. Very limited training and experience is required to operate this system. The user can learn to operate the system easily with some direct hands on experience in a simple and straightforward manner. 

To calibrate a torque wrench it needs to be placed on the Sushma Torque Sensor-Reaction type and held firm by the adjustable tool holding fixture thereby enabling perfect horizontal alignment, connected to the rigid reaction bar.  

The connection between the torque tool and the tool holding fixture is designed to ensure self-alignment, reduce parasitic forces, and moments to minimum levels, helping in better reading of uncertainty. 

The main rigid torque loading rig consists of the servo motor driven system with a highly precise gearbox which rotates the sensor in turn loading the torque wrench. 

The 7-inch touch Smart Control & Display Unit controls the entire machine and gives the user automated & guided instructions so as to take necessary actions. It also has a database to quickly recalibrate the tool without having to type all the details again (it can be coupled with the optional bar code scanner). The results from the test are then stored on the device, which can be viewed on the display or downloaded to PC through a USB or pen drive. 

You can upgrade to a Computer Automated System anytime by purchasing the PC Software & PC Package. The PC Software in the upgrade pack helps the user print calibration reports after all uncertainty calculations. It also has an audit mode to verify the uncertainty calculations. 

The TWC-205/206 is also future ready or comes with Internet of Things (IOT) Ready features enabling to connect to the Online Sushma Analytics Platform which will allow further analysis from various mobile devices which can be used for Quality, Productivity, Research or any other decision-making process. 

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