When it comes to torque wrench calibration, I often get asked “When should I re-calibrate my torque wrench? And should I wind it back to zero after use?” In fact, these two questions might well be the most frequently asked of all frequently asked questions and are rightly a subject of genuine concern for production and quality managers. To misuse the old wartime propaganda slogan a little, “Careless torque can cost lives.” When it comes to matters of recalibration, I always refer back to the standard BS EN ISO6789 – “Assembly tools for screws and nuts – Hand Torque Tools – Requirements and test methods for design conformance testing, quality conformance testing and recalibration procedure”.  Unsurprisingly, most of us refer to it as “the torque wrench standard”! In 1992, ISO 6789 was very much a document covering the design and manufacture of torque tools and the requirement was that the tool should be tested at maximum capacity for 500 ...

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