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Difficulty: MediumBolts, Nuts, and Washers

An automotive mechanic is selecting hardware to secure a replacement engine mount bracket and requires fasteners with an SAE Grade 5 rating. Which markings on the top of a steel bolt head designate an SAE Grade 5 bolt?

  1. A
    Five radial lines stamped on the bolt head
  2. Three radial lines stamped on the bolt headAnswer
  3. C
    No radial lines stamped on the bolt head
  4. D
    Six radial lines stamped on the bolt head

Answer

Three radial lines stamped on the bolt head
Under the SAE standard bolt grading system, the tensile strength grade of a standard hex bolt is calculated by adding 2 to the number of radial lines stamped on the head. Therefore, a bolt with three radial lines represents an SAE Grade 5 fastener (3+2=53 + 2 = 5), which is medium-strength carbon steel commonly used in automotive applications.

Step-by-Step Solution

1
Recall the SAE bolt head marking formula for tensile strength grading.
The rule states: SAE Grade=Number of Radial Lines+2\text{SAE Grade} = \text{Number of Radial Lines} + 2.
SAE (Society of Automotive Engineers) standardizes steel bolt tensile ratings using radial slash marks on the top of the hex head.
2
Determine the number of radial lines required for an SAE Grade 5 bolt.
Radial Lines=5−2=3\text{Radial Lines} = 5 - 2 = 3.
Subtracting 2 from the target grade of 5 yields 3 radial lines.

Key Concept

SAE Bolt Grade Identification by Radial Head Markings
Estimated Time:1m 0s
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Topics

Bolts, Nuts, and Washers

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