The load indicating washer is a precise fool-proof and economic device that ensures the automatic tightening of high strength friction grip bolts to the required shank tension.

It is merely a hardened washer with a series of protrusions on one face.  Induced bolt tension is indicated directly and so time is saved not only in tightening but in inspection.  You are assured of maximum consistency in bolt tensions with a minimum of operator skill.

As the bolt is tightened the protrusions are flattened and the gap reduced.  At a specific average gap measured by a feeler gauge as fig 2 the induced shank tension will not be less than the minimum required by standards.

Load Indicator Fitting  Inch Series   Metric Series

    General Grade  General Grade Part 1

Black Finish   0.015 in  0.40 mm

All Platings except Spun Galv 0.015 in  0.40 mm

Spun Galv   0.010 in  0.25 mm

Under nut with nut face washer 0.010 in  0.25 mm

(black and all nut face washer platings)

Fig. 1

Fig. 2

Thru Hardened Washer

HSFG Bolt Dimensions

High Strength Friction Grip BS4395: Part 1:1969

What is High Strength Friction Grip ?

Data Sheet 3

The term 'high strength friction grip bolts' relates to bolts of high tensile steel, used in conjunction with high tensile steel nuts and quenched and tempered steel washers, which are tightened to a predetermined shank tension in order that the clamping force thus provided will transfer loads in the connected members by friction between the parts and not by shear in or bearing on the bolts or piles of connected members.

Bolts shall be heat-treated under uniform conditions.  They shall be hardened by quenching in oil or water and shall then be tempered.

Bolts shall be identified as general grade high strength friction grip bolts by being marked with three radial lines 120 deg apart.  They shall also bear the manufacturers identification mark and in addition shall be marked 'ISOM' or 'M' to signify ISO metric thread.

Washers.  Flat round for use with the high strength grip bolts shall be identified by the provision of three nibs and an indented letter 'M' see Fig.1

Load Indicating Washer