Clamp Load

Clamp load is the compressive force that a tightened fastener applies to the parts being joined. When a bolt or screw is tightened, it stretches slightly and acts like a spring, pulling the joint members together. That squeeze between the parts is the clamp load, and it is what helps keep the joint from separating, slipping, or leaking under service loads.

Clamp load matters because it is more directly tied to joint reliability than torque alone. Torque is just the input, and much of it is lost to friction in the threads and under the head or nut, so the same torque can produce very different clamp loads depending on lubrication, coatings, surface finish, and fastener condition. Too little clamp load can lead to joint movement, loosening, and fatigue, while too much clamp load can crush materials, strip threads, or yield the fastener.