Identification Markings on Bolt Heads
ASTM and SAE Standards

Grade
Marking
Spec. Material Bolt &
Screw Size
Proof
Load
PSI
Tensile
Strength
Min PSI
SAE-Grade 1  Low Carbon Steel  1/4" - 1-1/2"  33,000 60,000
ASTM-A307 Low Carbon Steel  1/4" - 1/2" 
1-1/2" - 4"  
33,000 60,000
55,000 
SAE-Grade 2  Low Carbon Steel  1/4" - 3/4"
3/4" - 1-1/2" 
55,000
33,000 
74,000
60,000 
SAE-Grade 3  Medium Carbon Steel,
Cold Worked  
1/4" - 1-1/2"
 1/2" - 5/8" 
85,000
80,000 
110,000
100,000 
SAE-Grade 5
ASTM-A 449 
Medium Carbon Steel,
Quenched & Tempered 
1/4" - 1"
Over 1" - 1-1/2"
Over 1-1/2" - 3" 
85,000
74,000
55,000 
120,000
105,000
090,000
ASTM-A 325  Medium Carbon Steel,
Quenched & Tempered 
1/2", 5/8", 3/4"
7/8", 1"
1-1/8" - 1-1/2" 
85,000
78,000
74,000 
120,000
115,000
105,000 
ASTM-A 354
Grade BB 
Low Alloy Steel,
Quenched & Tempered 
1/4" - 2-1/2"
Over 2-1/2" - 4" 
80,000
75,000 
105,000
100,000 
ASTM-A 354
Grade BC
Low Alloy Steel,
Quenched & Tempered 
1/4" - 2-1/2"
Over 2-1/2" -4" 
105,000
095,000 
125,000
115,000 
SAE-Grade 5.1 Low or Medium Carbon 
Steel, Quenched & Tempered,
with Assembled Lock Washer 
Up to 3/8" incl. 85,000 120,000
SAE-Grade 7
Medium Carbon Alloy Steel,
Quenched & Tempered,
Roll Threaded
after Heat Treatment 
1/4" - 1-1/2" 105,000 133,000
SAE-Grade 8 Medium Carbon Alloy
Steel, 
Quenched & Tempered 
1/4" - 1-1/2" 120,000 150,000
ASTM-A 354
Grade BD 
Alloy Steel,
Quenched & Tempered 
1/4" - 1-1/2" 120,000 150,000
ASTM-A 490 Alloy Steel,
Quenched & Tempered 
1/2" - 2-1/2"
Over 2-1/2" - 4" 
120,000
105,000 
150,000
140,000 
Index