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Difficulty: EasyBolts, Nuts, and Washers

A technician is selecting replacement hardware for an equipment bracket and inspects a box of standard Unified National coarse (UNC) hex bolts marked with the specification 3/8-16 x 1-1/2. What does the number 16 indicate in this standard fastener callout?

  1. A
    Tensile strength grade rating of the steel
  2. Number of threads per inch along the bolt shankAnswer
  3. C
    Metric socket size in millimeters required for the bolt head
  4. D
    Total length of the bolt shaft in sixteenths of an inch

Answer

The number 16 indicates the number of threads per inch (TPI) along the bolt shank.
In standard Unified National fastener designations, the number immediately following the nominal diameter indicates the thread pitch, defined as the number of threads per inch (TPI). A 3/8-16 bolt has 16 complete thread ridges per linear inch of threaded shank.

Step-by-Step Solution

1
Break down the standard Unified National fastener notation format: Major Diameter - Threads Per Inch x Length.
In the callout 3/8-16 x 1-1/2, '3/8' is the nominal bolt diameter in inches, '16' is the thread density, and '1-1/2' is the length under the head in inches.
Standard SAE fastener specifications always present dimensions in the sequence of diameter, thread pitch (threads per inch), and overall length.

Key Concept

Standard Unified National (SAE) bolt dimension and thread nomenclature.
Estimated Time:45s
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Topics

Bolts, Nuts, and Washers

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