IS 10001 covers structural washers used with HSFG (High Strength Friction Grip) bolts per IS 3757. Larger and thicker than ordinary washers to distribute bolt load over the connection surface. Hardened to prevent relaxation under bolt pre-tension.
Specification for large structural washers for use with high strength bolts in steel structure connections.
Key Values
M20 washer OD37mm
M20 washer thickness4mm
M24 washer OD44mm
Practical Notes
! Always use IS 10001 structural washers with HSFG bolts — standard IS 2016 washers are too thin and soft.
! One washer under bolt head AND one under nut is mandatory for HSFG connections.
! Hardness must be 30-40 HRC — soft washers allow bolt relaxation and loss of pre-tension.
! Never reuse structural washers — they deform under HSFG bolt tension.