SAE J429 Excerpt - Mechanical and Chemical Requirements for Fasteners

This SAE standard contains mechanical and material requirements for UNC/UNF steel fasteners, used in the automotive industry and related industries up to size 1 1/2".

The standard does not contain requirements such as:

 

    • ability to withstand temperatures above +300°C or below at -50°C

 

MECHANICAL CHARACTERISTICS AND IDENTIFICATION SYMBOLS

Mechanical characteristics Resistance classes
Thread diameter Grade 2 Grade 5 Grade 8
>=1/4 <=3/4 >=3/4 <=1-1/2 >=1/4 <=1 >1 <=1-1/2 >=1/4 <=1
Test load on whole screw psi min. 55,000 33,000 65,000 74,000 120,000
Breaking load on whole screw psi min. 74,000 60,000 120,000 105,000 150,000
Yield strength on test piece psi min. 57,000 36,000 92,000 81,000 130,000
Breaking load on test tube psi min. 74,000 60,000 120,000 105,000 150,000
Test tube stretching % min. 18 18 14 14 12
Contraction on test tube % 35 35 35 35 35
Surface hardness Rockwell 30N Max - - 54 50 58.6
Rockwell core hardness min. B80 B70 C25 C19 C33
Rockwell core hardness Max B100 B100 C34 C30 C39
Marking from class None None

 

 

CHEMICAL ANALYSIS

Grade Diameter in inches
 Material and heat treatment Chemical composition Tempering temperature
C Mn P S B 1)
Min. Max Min. Max Max Max
2 >=1/4 <=1-1/2 Low or medium carbon steel 0.15 0.55 - 0.030 0.050 0.003
5 >=1/4 <=1-1/2 Medium carbon steel, quenched and tempered 0.23 0.55 - 0.030 0.050 0.003 427°C
8 >=1/4 <=1-1/2 Medium carbon alloy steel quenched and tempered 2) 0.28 0.55 - 0.030 0.050 0.003 427°C

1) the boron content can reach 0.005% as long as the ineffective boron is controlled by the addition of titanium and/or aluminum.

2) When agreed between manufacturer and buyer, medium carbon steel can be used for products with nominal diameter of 7/16 in. and smaller, and medium carbon steel with boron for products with nominal diameter of 1 in. and smaller.