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Difficulty: MediumBolts, Nuts, and Washers

A technician is replacing hardware on a heavy-duty truck trailer hitch assembly that specifies high-tensile SAE Grade 8 bolts. When sorting through hex-head fasteners in the shop inventory, which bolt head marking correctly identifies an SAE Grade 8 fastener?

  1. A
    Eight radial slash marks evenly spaced around the head
  2. B
    Three radial slash marks spaced 120 degrees apart
  3. Six radial slash marks evenly spaced around the headAnswer
  4. D
    A smooth head with no radial slash marks

Answer

Six radial slash marks evenly spaced around the head
For standard SAE inch-series steel bolts, the tensile strength grade is determined by counting the radial slash marks stamped on the bolt head and adding 2 (Grade=radial lines+2\text{Grade} = \text{radial lines} + 2). An SAE Grade 8 bolt has 6 radial lines (6+2=86 + 2 = 8), indicating a minimum tensile strength of approximately 150,000 psi.

Step-by-Step Solution

1
Recall the SAE bolt head grading formula for standard inch-series hex-head bolts.
The formula is SAE Grade=Number of Radial Lines+2\text{SAE Grade} = \text{Number of Radial Lines} + 2.
SAE standard J429 defines tensile strength categories by radial tick marks on the bolt head starting with Grade 5 (3 lines) and Grade 8 (6 lines).
2
Calculate the required number of radial lines for an SAE Grade 8 bolt.
Radial Lines=8−2=6\text{Radial Lines} = 8 - 2 = 6.
An SAE Grade 8 bolt requires 6 radial slash marks stamped into the top of the hex head.

Key Concept

SAE Hex Bolt Grade Identification via Radial Lines
Estimated Time:45s
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Topics

Bolts, Nuts, and Washers

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