Torque Wrenches

What is Torque?

Torque is any force or system of forces that tends to cause rotation about an axis.

Measurement of Torque

Imagine someone tightening a bolt using a socket attached to a meter long bar. If they apply 10 kg of force (kgf) perpendicular to the bar they will produce a torque of 10 kgf.m at the axis (the centre of the bolt). However, under the S.I. system of measurement, force is expressed in Newtons (N) rather than kgf. The conversion between kgf and N is x 9.807 so the person is applying 98.07 N.m of torque.

The Importance of Torque Control

Although many methods exist to join two or more parts together, the ease of assembly and disassembly provided by threaded fasteners make them the ideal choice for many applications.

The object of a threaded fastener is to clamp parts together with a tension greater than the external forces tending to separate them. The bolt then remains under constant stress and is immune from fatigue. However, if the initial tension is too low, varying loads act on the bolt and it will quickly fail. If the initial tension is too high, the tightening process may cause bolt failure. Reliability therefore depends upon correct initial tension. The most practical way of ensuring this is by specifying and controlling the tightening torque.

Bolt Tension

When an assembly is clamped by tightening a nut and bolt, the induced tension causes the bolt to stretch. An equal force acts to compress the parts which are thus clamped. The proof load of a bolt, normally established by test, is the load which just starts to induce permanent set – also known as the yield point. Typically bolts are tightened to between 75% and 90% of yield.

Torque Wrenches

Norbar - Professional Torque Wrench

Since its original, award winning launch in 1984 and extensive face-lift in 2000, Norbar’s Professional torque wrench range has become one of the most popular wrench ranges available worldwide. In this re-engineered version, the core principles of accuracy, durability and comfort are carried over but every component part is new and improved.

TTi Wrench : Models 20 N.m and 50 N.m

Durability has been a primary development goal – both in terms of the lifetime of components and longevity of calibration accuracy. Cycle testing of wrenches at full torque was a key element of the development process and, in total, several million tightening cycles were accumulated. The result is a product that you can use with complete confidence that you have the best tool for the job.

NorTronic® Electronic Torque Wrench

Introducing NorTronic® - The first electronic torque wrench from Norbar. Precise, Wireless and traceable.

Professional Torque Wrench : Production ‘P’ Types

'P' Type wrenches are designed for the production environment where they will be set and then dedicated to a particular application. There is no scale, the wrench must be set against a torque testing device such as Norbar's Professional Torque Tester.

Slimline™ Torque Wrench : Model SLO Fixed Head & Torque Handles
  • Accuracy exceeds all international standards.
  • Unmistakable signal when set torque is reached.
  • Traceable calibration certificate supplied to satisfy ISO 9000:2000 quality systems.
Slimline™ Torque Wrench : Model SLO ‘P’ Type
  • Torque Handle versions are available for both 16mm spigot and 9 x 12mm fittings.
  • Production 'P' type versions are designed to discourage unauthorised alteration.
Industrial Torque Wrench : Adjustable Models
  • Robust construction gives accurate results, to ±4%, even in arduous working conditions.
  • Every wrench supplied with a calibration certificate to satisfy requirements of ISO 9000:2000.
Industrial Torque Wrench : Torque Handles, Production ‘P’ Type and Split Models
  • Robust construction gives accurate results, to ±4%, even in arduous working conditions.
  • Every adjustable wrench supplied with a calibration certificate to satisfy requirements of ISO 9000:2000.
  • The break angle improves accuracy by reducing the possibility of over torquing.