Difference between fastener standard for bolts IS1367Gr. 4.6, 8.8

 This is fastener standard for bolts:

Grade 8.8 means, Approx. 800 Mpa tensile strength and 640 MPa yield strength (you will arrive at the YS by multiplying both the numbers times 10. That is 8x8x10=640)

Similarly, 10.9 means approx.1000Mpa TS and 900 Mpa yield strength. See the below-given details.

The grade 8.8 refers to the tensile strength which is generally 116,000 psi, grade 10.9 is generally 150,000 and grade 12.9 is generally 175,000 psi. Grade 8.8 high tensile steel is often referred to as the structural grade for bolts.

Material	Property Class	Tensile Strength, Mpa	Hardness	Heat Treatment	Tempering
Low or medium carbon steel with max limits for C 0.55, P0.048, S0.058	4.6	400	B67-B87	No
Low or medium carbon steel with max limits for C 0.55, P0.048, S0.058	4.8	420	B71-B87	No
Low or medium carbon steel with max limits for C 0.55, P0.048, S0.058	5.8	520	B82-B95	No
Medium carbon steel with max   limits for C0.28- 0.55, P0.048, S0.058	8.8	830	C23-C34	Oil Quenched	min 425°C
Medium carbon steel with max   limits for C0.28- 0.55, P0.048, S0.058	9.8	900	C27-C36	Oil Quenched	min 410°C
Medium carbon steel with max   limits for C0.28- 0.55, P0.048, S0.058	10.9	1040	C33-C39	Oil Quenched	min425°C
Medium carbon steel with max   limits for C0.31- 0.65, P 0.045 MAX, S 0.045MAX	12.9	1220	C38-C44	Oil Quenched	min 380°C