Figure 7-7. Nomograph for Torque on Bolts (7-6)
The size, number and spacing of the fasteners should be sufficient to establish the required bonding pressure
over the entire joint area. The pressure exerted by a bolt is concentrated in the immediate vicinity of the bolt
head. However, large, stiff washers can be placed under the bolt head to increase the effective contact area.
Because the load is distributed over a larger area, the tensile load on the bolt should be raised by increasing the
torque. The nomograph of Figure 7-7 may be used to calculate the necessary torque for the size bolts to be
used. Where the area of the mating surfaces is so large that unreasonably high bolt torques are required, more
than one bolt should be used. For very large mating areas, rigid backing plates should be used to distribute the
force of the bolts over the entire area.
Riveted bonds are less desirable than bolted connections or joints bridged by metal flow processes. Rivets lack
the flexibility of bolts without offering the degree of protection against corrosion of the bond surface that is
achieved by welding, brazing or soldering. The chief advantage of rivets is that they can be rapidly and
uniformly installed with automatic tools.