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Torque Control

Guide

Tightening torque and tensile load

Nouveau ContenuImageApplication of the correct force (tensile load) is essential for a reliable assembly:

  • undertight fasteners can work loose;
  • overtight fasteners may distort components or shear.

Tensile load depends on tightening torque and friction coefficient.

Tensile load (Fo)
The force in newtons (N) which maintains pressure contact between assembled components.

Tightening torque (Cs)
The product of a force and the leverage length at which it is applied: Torque (Nm) = Force (in newtons) x Length (in metres).

How tight a torque ?

1. Always observe equipment manufacturer's specifications.
2. If none are available, determine required torque on a test rig.
3. Otherwise, refer to national standards.

  • Tightening torque table
Torque values are given for 85% fastener yield strength, for class "A" torque control accuracy (< ±5%).

1. Friction coefficient
Actual friction coefficient depends on fastener and component condition, and affects tightening. Choose the appropriate table according to type of fasteners used (i.e. µ = 0,10, 0,15 or 0,20).

2. Fastener grade
The grade of a fastener denotes its quality (best is 12.9). Check the appropriate column for the fasteners used.

3. Tightening torque (Cs)
Torque values are listed in newton-metre (Nm) for each type of fastener.

4. Tensile load (Fo)
This force in newtons (N) is the equivalent of an Fomax value.

The above information, for which Facom accepts no liability, is given as a guide only.

Conversion table : The internationally accepted unit is the newton-metre (Nm)

 1. To convert Nm : 

  • Newton metres to kilogramme force metres : 1 Nm = 0,102 kgf m
  • Newton metres to pound force feet : 1 Nm = 0,738 lbf ft
  • Newton metres to pound force inches : 1 Nm = 8,851 lbf in
  • Newton metres to ounce force inches : 1 Nm = 141,61 ozf in  

 2. To convert kgf m: 
  • Kilogramme force metres to newton metres : 1 kgf m = 9,81 Nm
  • Kilogramme force metres to pound force feet : 1 kgf m = 7,23 lbf ft
  • Kilogramme force metres to pound force inches : 1 kgf m = 86,8 lbf in  

 3. To convert lbf f:
  • Pound force feet to newton metres : 1 lbf ft = 1,35 Nm
  • Pound force feet to kilogramme force metres : 1 lbf ft = 0,138 kgf m
  • Pound force feet to pound force inches : 1 lbf ft = 12 lbf in  

 4. To convert lbf in: 
  • Pound force inches to newton metres : 1 lbf in = 0,1129 Nm
  • Pound force inches to kilogramme force metres : 1 lbf in = 0,0115 kgf m
  • Pound force inches to pound force feet : 1 lbf in = 0,083 lbf ft
  • Pound force inches to ounce force inches : 1 lbf in = 16 ozf in 

 

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