Visual ID Description Material Tensile Strength
No lines
Unmarked
Intermediate
Quality
SAE Grades 0-1-2
Low Carbon Steel 65,000 p.s.i.
3 Lines -
Common
commercial
quality
Automotive and
AN Bolts
SAE Grade 5
Med. carbon steel
Tempered
120,000 p.s.i.
4 Lines -
Medium
commercial
quality
Automotive and
AN Bolts
SAE Grade 6
Med. carbon steel
Quenched &
tempered
140,000 p.s.i.
5 Lines -
rarely used
SAE Grade 7
Med. carbon alloy
steel
140,000 p.s.i.
6 Lines -
Best
commercial
quality
N.A.S. & Aircraft
SAE Grade 8
Med. carbon alloy
steel Quenched
and tempered
150,000 p.s.i.
Supertanium Special alloy
steel
Quenched &
tempered
160,000 p.s.i.
A-354-BD
A490
Med. Carbon
alloy steel
Quenched &
tempered
150,000 p.s.i.
Socket head
cap screw
Also N.A.S.
Aircraft
standard
High carbon
Quenched &
tempered
160,000 p.s.i.
N.A.S. 144
Aircraft
standard
steel
High carbon
Quenched &
tempered
160,000 p.s.i.
N.A.S. 624
National
aircraft
standard
steel
High carbon
Quenched &
tempered
180,000 p.s.i.
Aircraft
No number
assigned steel
High carbon
Quenched &
tempered
220,000 p.s.i.