A click wrench has a calibrated mechanical cam that resists movement until a set torque is reached. A dial wrench has a spring that translates torque into motion on a calibrated dial. Fastening experts warn that residual torque and dynamic torque are not identical. Residual torque is often lower than dynamic torque. In many cases, the joint relaxes after being fastened.
Joint relaxation occurs to some extent in all fastened joints.
One part embeds into another. A layer of paint, a spring washer or a soft part, such as an O-ring, compresses under the clamp force. This relaxation, or creep, is most obvious and dramatic right after force has been applied. In most joints, creep appears within the first 10 to 50 milliseconds. However, some joints can take a long time to settle.