Screw Thread Strength Calculator v1

Price: £19.06 (£19.06 Inc. VAT)
Screw thread strength calculator


Whilst the history of the screw thread can be traced in various forms back to Archimedes, the thread we know today was designed and standardised by John Whitworth in the early 1840s. It is based upon a 60⁰ included angle and all of today’s standard designs are based upon his original.

It is interesting to note that just like Stephen Morse, John Whitworth also came up with 3⁰ as the best contact angle for his thread (see technical help). Moreover, his standard sizes were designed to provide the same strength in the body and the thread of properly manufactured screws and bolts.


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The screw thread strength calculator contains a comprehensive database of basic dimensions for metric and Imperial standard engineering screw threads including BA, UN, UNEF, UNF, UNC, UNS, BSW & BSF, and calculates strengths and torque rates for the thread you select based upon your input data for material strength and friction coefficient.

Threads also calculates the torque needed to tighten the selected thread to between 20% and 100% of bolt strength.

Screw Thread Strength Calculator - Options

For all calculation options the input and output data are as follows:

You enter: and the screw thread strength calculator will provide:
  • Yield strength of the bolt material
  • Coefficient of friction between the mating threads
  • wire diameters for thread measurement
  • All thread dimensions
  • Cross-sectional area (at thread root)
  • Maximum axial force
  • Torques required to tighten the thread to 20%, 40%, 50%, 60%, 80%, 90% and 100% of tensile capacity calculated according to API recommendations
  • Measurement across wires

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