Question

1. Write a short note explaining how to identify as to which SAE Grade / Class steel is used for making bolt and screws.

Answer 1

SAE Bolt Grades—The standards for bolt strength grades in the U.S. are set according to a system developed by the SAE (Society of Automotive Engineers.) The SAE marking system uses raised dashes on the bolt head to indicate strength.

Most fasteners are made from steel. Specifications cover a broad range of mechanical properties that are indicated by a bolt-head marking system that identifies the fastener by grade. For example, SAE grades 2, 5, and 8 are most often specified. Common steels are SAE 1010 (machine screws, carriage bolts, and other fasteners without critical strength requirements); SAE 1018, 1020, 1021 (bright cap screws, special items); SAE 1038 (high-strength bolts, studs, nuts, cap screws); SAE 1041, 1045, 1330, 1340 (special high-strength requirements), and SAE 1100 series (resulfurized -- usually for nuts).

here is very simple table i am presenting for identification of class of steel:-

SAE Grade	Head Marking	Size Range (in)	Minimum Proof Strength (103 psi)	Minimum Tensile Strength (103 psi)	Material
1		1/4 - 1 1/2			Low - medium carbon steel
2		1/4 - 3/4 7/8 - 1 1/2	55 33	74 60	Low - medium carbon steel
5		1/4 - 1 1 1/8 - 1 1/2	85 74	120 105	Medium carbon steel, Q & T
5.2		1/4 - 1	85	120	Low carbon martensite steel, Q & T
7		1/4 - 1 1/2	105	133	Medium carbon alloy steel, Q & T
8		1/4 - 1 1/2	120	150	Medium carbon alloy steel, Q & T
8.2		1/4 - 1	120	150	Low carbon martensite steel, Q & T

SAE J429 is the standard specification for inch-series steel bolts, screws, studs, SEMS screws and U-bolts in sizes up to and including 1-1/2 inches. They are generally manufactured from variants of medium carbon steel. SAE J429 bolts from Glaser and Associates are available in three grades, 2, 5 and 8, offering different mechanical and chemical properties for specific applications.

These bolts are designed, manufactured and tested to comply with the standards set by SAE J429 for proof load, yield strength, tensile strength, elongation, surface roughness and core hardness.

Grades

• Grade 2 – bolts manufactured from low or medium carbon steel.
• Grade 5 – bolts manufactured from medium carbon steel.
• Grade 8 – bolts manufactured from medium carbon alloy steel.

The properties tables below provide more information on the differences between the grades.

Applications

SAE J429 bolts from Glaser and Associates meet the mechanical and material requirements for fasteners used in the automotive and related industries. For applications that require specific levels of fatigue behavior, corrosion resistance or impact properties, please consult our technical department.

Properties

Grade	Nominal size, inches	Full size proofload, psi	Yield strength, min, psi	Tensile strength, min, psi	Elong, min, %	RA, min, %	Core hardness, Rockwell
2	¼ - ¾ inch	55,000	57,000	74,000	18	35	B80 to B100
¾ - 11/2 inch	33,000	36,000	60,000	18	35	B70 to B100
5	¼ - 1 inch	85,000	92,000	120,000	14	35	C25 to C34
1 - 1-1/2 inches	74,000	81,000	105,000	14	35	C19 to C30
8	¼ - 1-1/2 inches	120,000	130,000	150,000	12	35	C33 to C39

Grade	Material	Carbon, %	Phosphorus, %	Sulfur, %
2	Low or medium carbon steel	0.15 - 0.55	0.030 max	0.050 max
5	Medium carbon steel	0.28 - 0.55	0.030 max	0.050 max
8	Medium carbon alloy steel	0.28 - 0.55	0.030 max	0.050 max