What is the difference between Grade C and Grade A/B bolts?

Grade C indicates lower precision and wider dimensional tolerances (commercial finish) compared to the tighter tolerances of Grades A and B.

How do you designate a bolt according to this standard?

A typical designation includes the name, IS number, thread size, nominal length, and property class (e.g., Hexagon head bolt IS 1363 (Part 1) - M12 x 80 - 4.6).

Where can I find the tensile strength requirements for these bolts?

Tensile strength and other mechanical properties are specified in IS 1367 (Part 3), not in IS 1363.

IS 1363 Part 1

: 2002

Hexagon Head Bolts, Screws and Nuts of Product Grade C - Part 1: Hexagon Head Bolts (Size Range M 5 to M 64)

CurrentFrequently UsedSpecificationGeneral · Steel and Reinforcement

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This standard specifies the dimensions, characteristics, and designation of hexagon head bolts of product grade C (commercial/black bolts) in the size range of M5 to M64 used for general engineering applications.

Specifies requirements for hexagon head bolts of product grade C, with sizes M 5 to M 64.

Quick Reference Values

Minimum nominal thread diameterM 5

Maximum nominal thread diameterM 64

Product gradeGrade C

Typical property class4.6

Practical Notes

Grade C bolts are widely known as 'black bolts'. They have wider dimensional tolerances compared to Grades A and B.

These fasteners are primarily used in clearance holes for static loads and secondary structural connections where high precision is not mandatory.

This standard only dictates dimensions; the mechanical properties and testing (like yield strength and ultimate tensile strength) must be referred to IS 1367.