In the process of installing a chain drive system, the motor and driven component should be checked for a soft foot condition and excessive run-out. The shaft run-out should be no more than __________.

• A. 0.002 inches
• B. 0.01 inches
• C. 0.005 inches
• D. 0.0005 inches

Answer: (A)

Maintaining straight, true rotation is essential for a reliable chain drive. Soft foot means the mounting surfaces aren’t perfectly flat, so when you tighten the bolts the equipment can tilt slightly. That tilt pushes the shafts off axis, and as you rotate, any wobble (run-out) translates into belt and pulley misalignment, increasing side loading, vibration, wear, and bearing stress. To prevent these problems, the shaft run-out must be kept within a very tight limit. The standard maximum is 0.002 inches. This strict tolerance helps keep pulleys concentric and the chain engagement smooth, reducing dynamic forces and extending bearing and belt life. If run-out were looser, such as 0.01 inches, misalignment would be substantial; 0.005 inches is better but still looser than the preferred spec; 0.0005 inches would be exceedingly difficult to achieve in most setups and not typically required by standard practice. So, 0.002 inches is the most appropriate maximum.