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Torque 'N' Tension Technology
The use of torque (turning or twisting force) has long been associated with methods of tightening and inspecting bolts. The object of tightening bolts is to achieve a minimum tension (straight pull), not torque, in the bolts.
As a nut and bolt are tightened the components to be fastened are clamped together. The thread angle in the bolt converts the force applied into tension (or stretch) in the bolt shank. The amount of the tension created in the bolt is critical, because when a bolt is tensioned correctly it is working at its optimum efficiency and will resist coming undone.
- If the tension is too low the nut could vibrate or work loose.
- If the tension is too high (over-stretched), the bolt could break.
Most coatings designed for threaded fasteners, particularly in automotive applications, will need to meet demanding torque-tension requirements.
The relationship between the Torque, Tension and CoF forces is an important factor in ensuring a fastener secures a joint with maximum force, whilst remaining below the fasteners designed failure point (proof load).
Due to the very unpredictable friction values of zinc based coatings, torque-tension modifiers are frequently employed, especially on fasteners. These products are usually applied as part of the finishing process to ensure consistent friction properties.
Many different automotive torque/tension standards currently exist, however most requirements can be met using one of MacDermid's 6 popular friction control fluids.
Achieving the correct tension in fasteners is vital if a joint of fixing is to remain secure under load, without compromising the strength or integrity of the fastener or joint.
Torque: is a measurement of force, in this case the force required to turn and tighten a fastener to secure a joint.
Tension: is a measure of stored energy or stretch induced in a fastener once it is tightened.
Coefficient of Friction: is a term used for describing the material surface conditions that determine torque-tension.