TOPIC 3Design of Nonpermanent Joint: BOLT

JOINT

Shigley’s Mechanical Engineering Design

9th Edition in SI unitsRichard G. Budynas and J. Keith Nisbett

Prepared by

Afandi DzakariaFaculty of Mechanical Engineering

UNIVERSITI TEKNOLOGI MALAYSIA

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Thread Terminology

• The terminology of screw threads is explained as follows:� The pitchpitchpitchpitch is the distance between adjacent thread forms measured

parallel to the thread axis.� The major diameter major diameter major diameter major diameter d is the largest diameter of a screw thread.� The minor (or root) diameter minor (or root) diameter minor (or root) diameter minor (or root) diameter dr is the smallest diameter of a screw

thread.� The pitch diameter dp is a theoretical diameter between the major and

minor diameters.• A multiplemultiplemultiplemultiple----threadedthreadedthreadedthreaded product is one having two or more threads cut

beside each other.• All threads are made according to the rightrightrightright----hand rule hand rule hand rule hand rule unless

otherwise noted.

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Thread Profile

M10 x 1.5: (Metric Thread)

Metric threads are specified by writing the diameter and pitch in

millimeters. This thread have a nominal major diameter of 10 mm and

a pitch of 1.5 mm. (Table 8-1).

0.625"-18 UNRF : (Unified Thread)

Unified threads are specified by stating the nominal major diameter,

the number of threads per inch, and the thread series. (Table 8-2).

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Thread Types

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Thread Types

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Bolt Strength

• In the specification standards for bolts, the strength is specified by stating ASTM minimum quantities, the minimum proof minimum proof minimum proof minimum proof strengthstrengthstrengthstrength, or minimum proof loadminimum proof loadminimum proof loadminimum proof load, and the the the the minimum tensile minimum tensile minimum tensile minimum tensile strengthstrengthstrengthstrength.

• The proof load proof load proof load proof load is the maximum load (force) that a bolt can withstand without acquiring a permanent set. The proof proof proof proof strength strength strength strength is the quotient of the proof load and the tensile-stress area.

• 15 percent fastener fatigue failure under the head, 20 percent at thread runout, and 65 percent

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Bolt Strength

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Bolt Strength

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Bolt Strength

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Shear Load

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Axial Load

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Torsion Load

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Centroid Finding of Bolts

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Bending Load

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Shear Joint with Eccentric Loading

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Exercises

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Example 8-7

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Example 8-7

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Example 8-7

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Example 8-7