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Torque Table & Equations

Torque Table & Equations

torquetable

 

Download a PDF version of the chart here.

The above torque table was developed and simplified for marine applications, and is based on material strength.

 

Torque Table Equations

First, the units:

$$TPI$$  Threads Per Inch

$$d_{nom}$$  Nominal diameter

$$A_t$$  Tensile Stress Area

$$F_y$$  Yield Strength

$$F_i$$  Preload

$$S_p$$  Proof Strength

$$K$$  Coefficient of friction (=0.15 for lubricated screws)

 

To determine Preload:

$$F_i=0.75F_p$$  for non permanent connections1.

$$F_p=A_tS_p$$

$$S_p=0.85F_y$$  for proof strength

To calculate bolt torque:

$$T=KF_id$$

Which can also be written as:

$$T=(0.15)(0.75)A_t(0.85)F_yd_{nom}$$

References

  1.  Shigley’s Machine Design, 1998.  p. 427 (Eq. 8-30)
  2.  Shigley’s Machine Design, 1998.  p. 423 (Eq. 8-27)