How Transformations were occuring on Torque Measurements ?

Industrial Torque Measurements transformed from mechanical dial wrenches (analog) to Digital instruments.

40 years ago, it was highly unlikely that anything more sophisticated than, a mechanical dial torque wrench would have been used in Industrial Production line, to monitor applied torque on fasteners.

Torque Tools are for ensuring accuracy of torquing, practically.

Torque accuracy for Industrial Assembling

Industrial Assembling Tools - pneumatic, electric and hydraulic powered are used, to run fasteners, followed by final accurate torquing with a dial indicator or, more commonly a click action torque wrench. These wrenches give accuracy of +/-5% to +/-2%  indicating or set torque value.

Accuracy Need Realisation

Gradually, it was realised that it was more effective to monitor directly the torque output of power regulated assembly tools, rather than perform break-away checks on individual fasteners after they had been driven.

This accuracy need was addressed using a rundown fixture over the top of a static transducer, thus allowing the tool to go through its normal cycle of operation in a reasonably close simulation of actual joint conditions.

The rundown fixture or joint simulator (usually a cap screw passed through a stack of disc springs) connected to a square drive of a static transducer were used generally.

It is never a true recreation of the actual joint, but is a better representation than driving a tool directly on a bare transducer. This also saved life of Torque Transducers' accuracy. 

At that point was, pulse tools came into use.

These tools, which were originally developed from impact wrenches, are fast and reaction less, but accepted enough for normal production use.

They can be easily measured and verified using an external inline rotary transducer.

Still more accuracy...

Further need on measurement accuracy increased. Production lines realised that many of the assembly tools in use were simply not capable of maintaining the accuracy and repeatability, necessary for an efficient high quality production plants.Tools, both pneumatic and electric, were developed with inbuilt inline transducers for a controlled torque delivery to any critical joint, directly at production line.These were and still valuable for critical applications, but tended to be too expensive for general production work.

Torque and Angle

In addition to torque, an optical encoder inbuilt within transducer, measures angle as an extra parameter to aid tool assessment along with torque.

Most modern production lines now have a mix of transducerized tools and torque controlled tools which are periodically verified (on a weekly, daily or some places, hourly too (depending on the importance of the particular application) with help of various torque monitoring instruments or equipments.

Inline Torque transducers. 

Globally, industrial assembly lines or production lines started adapting inline torque testing. Torque measuring and monitoring tools became digital, mobile, repeatable and accurate handheld devices. While extremely portable, electronic and digital torque tools are with possibility for to be connected to static torque transducer, rotary torque transducer, digital torque wrench. 

Realtime continuous torque measurements.

Brushless transducers with inbuilt display and wireless data transmission features are on the rise on critical torque applications. For running variety of tests, analysis, and to map variation patterns, robust brushless transducers helps with tag of precision instruments. 

Torque Tools Calibration cycles 

All torque tools can be checked, verified, calibrated and recorded periodically.

Calibration could be achieved in accordance with ISO 6789 

Period can be defined, according to stringent quality parameters followed in accordance to meet industrial standards 

ISO recommended cycle: Every 5,000 cycles (or) 6 months - whichever occurs first

Existing calibration life has to be renewed, if cycle expired or undergone repair and reconditioning, or following a maintenance activity. 

Torque Tools classification for calibration

ISO 6789 classifies Torque tools to be calibrated into - 

1. Indicating Torque Tools 
2. Setting Torque Tools

Keep Torquing precisely.