Updated 04-May-2020.
Mondo shtuff from around the internet, all about TORQUE WRENCH!
My botty best at summarizing from Wikipedia: a torque wrench is a tool used to apply a specific torque to a fastener such as a nut or bolt . it is usually in the form of a socket wrench with special internal mechanisms . a torque wrench uses torque as a proxy for bolt tension . technique suffers from inaccuracy due to inconsistent or uncalibrated friction between fastener and mating hole . bahr was frustrated at the inconsistent tightness of flange bolts he found while attending to his work . he claimed to have invented the first torque limiting tool in 1918 . the first is a lever used to apply the torque to the fastener being tightened . the second beam is only attached at one end to the wrench head and free on its other, this serves as the indicator beam . both the beam type torque wrench was developed between late 1920s and early 1930s . the end of the indicating beam points to the magnitude of the torque being applied . this type of wrench is simple, inherently accurate, and inexpensive the beam type torque wrench employs the principle of applying torque to a deflecting beam rather than a coil spring . the operator can both hear the signal click and see a visible indicator when the desired torque is reached . the load carrying beam is straight and runs from head to handle, it deflects when torque is applied . the other beam (indicating beam) runs directly above the deflecting beam for about half of the length then bends away at a deflecting beam torque wrench is attached to a scale and onto that is fitted a wedge . this wedge is used to set the desired torque . from this side protrudes a pin, which acts as this firing makes a loud click and gives a visual indication that the desired torque has been met . the indicator pin can be reset by simply pressing it back into the indicating beam . if a torque is demanded which one common form uses a ball detent and spring, with the spring preloaded by an adjustable screw thread . this design yields greater precision as well as giving tactile and audible feedback . a modification of this design is the drill will start slipping once the desired torque is reached . they are usually T-handled wrenches with a one-way combination ratchet and clutch . the signal generated by the transducer is converted a number of different joints (measurement details or limit values) can be stored . these programmed limit values are then permanently displayed during the tightening process . the readings memory can then be easily transferred to a PC Typical accuracy level would be +/- 0.5% to 4% . angle is measured by an angle sensor or electronic gyroscope . inbuilt readings memory enables measurements to be statistically evaluated . this type of torque wrench can also be used to determine breakaway torque, prevail torque and the final torque of a tightening job . thanks to a special measuring process, it is also possible to display the yield point (y electronic and mechanical measurements are documented via wireless data transmission . users will know they have achieved the desired torque setting when the wrench “beeps” they are used for aviation and heavy machinery assembly . smaller hydraulic torque wrenches have a reaction arm built into the tool . larger models require other fixing arrangements in order to prevent rotation . smaller models have an reaction arm . that rests against another fastener pneumatic torque wrench is sometimes confused with a standard impact wrench due to their similar appearance . planetary torque multiplier gearboxes have multiplication ratios up to 125:1 . the torque output is adjusted by controlling the pneumatic torque wrench was first invented in Germany in the early 1980s . Torque capabilities range from 118Nm, up to a maximum of 47,600Nm . pneumatic motor using compressed air is the most ISO standard covers construction and calibration of hand-operated torque tools . defines two types of torque tool encompassing twelve classes . also given is the percentage allowable deviation from the desired torque . tools should be marked with their torque range and the unit of torque . direction of operation for unidirectional tools and the maker’s mark . if a calibration certificate is provided, the tool must be marked . the standard also separates manual and electronic tools into different sections and designations . the ASME and ISO standards cannot be considered compatible . table below gives some of the types and tolerances specified by the standard . scale on a beam type wrench is prone to parallax error, as a result of the large distance between indicator arm and scale . there is also the issue of increased user error with the beam type . using handle ISO standards calibration should happen every 5000 operations or every year, whichever comes first . never set a micrometer style torque wrench to zero as the internal mechanism requires a small amount of tension . torque wrenches can fall up to 10% out of calibration in the first year of use . the operation requires specialist torque wrench calibration equipment with an accuracy of 1% or better . temperature of the area where calibration is performed should be professional calibration is recommended, but for some people it would be out of their means . it is possible to calibrate a torque wrench in the home shop or garage . the error within the tool can be calculated and the tool may be