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Question 15.5: Determining the Torque to Generate a Bolt Preload Problem Fi...

Determining the Torque to Generate a Bolt Preload

Problem    Find the torque required to preload the bolt in Example 15-3.

Given    A 5/16-18 UNC-2A, grade 5.2 bolt, 2.5 in long, preloaded to 90% of proof strength with an axial force of 4 011 lb.

Assumptions    The threads will be lubricated. Assume a coefficient of friction of 0.15.

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1    The required tightening torque can be estimated with equation 15.23d:

T_i \cong 0.21 F_i d=0.21(4011)(0.3125)=263  lb -\text { in }      (a)

2    The files EX15-05 can be found on the CD-ROM.

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