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Difficulty: MediumBolts, Nuts, and Washers

A shop technician is organizing carbon steel hex-head fasteners by their load-bearing capacity before restocking service bins. Arrange the following SAE bolt head markings in order from lowest minimum tensile strength to highest minimum tensile strength.

  1. 1Bolt head with no radial lines (plain, unmarked head)
  2. 2Bolt head stamped with 3 radial lines
  3. 3Bolt head stamped with 5 radial lines
  4. 4Bolt head stamped with 6 radial lines

Answer

Plain/unmarked head (Grade 2), followed by 3 radial lines (Grade 5), then 5 radial lines (Grade 7), and finally 6 radial lines (Grade 8).
SAE bolt strength is identified by counting the radial lines on the hex head and adding 2. An unmarked bolt head is SAE Grade 2 (~74,000 psi), 3 radial lines designate SAE Grade 5 (~120,000 psi), 5 radial lines designate SAE Grade 7 (~133,000 psi), and 6 radial lines designate SAE Grade 8 (~150,000 psi). Arranging them from lowest to highest tensile capacity yields: unmarked bolt, 3 radial lines, 5 radial lines, and 6 radial lines.

Step-by-Step Solution

1
Identify the standard rule for determining SAE bolt grades from head markings.
The SAE grade equals the number of radial hash marks plus 2 (Grade = Lines + 2). An unmarked head represents SAE Grade 2.
SAE standard J429 defines fastener tensile strength categories by the count of radial lines embossed on the bolt head.
2
Calculate the SAE grade and corresponding minimum tensile strength for each fastener marking.
Unmarked = Grade 2 (74000 psi74{}000\text{ psi}); 3 lines = Grade 5 (120000 psi120{}000\text{ psi}); 5 lines = Grade 7 (133000 psi133{}000\text{ psi}); 6 lines = Grade 8 (150000 psi150{}000\text{ psi}).
Fastener strength increases sequentially with higher grade numbers.
3
Arrange the fasteners in ascending order from lowest tensile strength to highest tensile strength.
Item with no radial lines → Item with 3 radial lines → Item with 5 radial lines → Item with 6 radial lines.
This orders the bolts from lowest load capacity (74000 psi74{}000\text{ psi}) to highest load capacity (150000 psi150{}000\text{ psi}).

Key Concept

SAE Bolt Grade Identification and Tensile Strength Hierarchy
Estimated Time:1m 0s
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Topics

Bolts, Nuts, and Washers

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