The most often used fastener to attach a motor to a bed-plate is a hex head bolt with which combination?

• A. Two Flat Washers and a Nut
• B. Lock Washer and Nuts
• C. A Bolt With a Spring Washer
• D. Two Flat Washers, a Lock Washer and a Nut

Answer: (D)

Vibration from a running motor tends to loosen fasteners, so the attachment needs parts that both distribute load and resist rotation. Two flat washers spread the clamping load across the mating surfaces and protect them from damage, one on each side of the bed-plate. A lock washer adds a bite into the surfaces to resist turning under vibration, helping maintain the clamp force. The nut then secures the bolt in place. Using this combination—two flat washers, a lock washer, and a nut—gives a robust, vibration-resistant connection for a hex head bolt attaching a motor to a bed-plate. Without the lock washer you risk loosening; without the extra flat washers you risk uneven load distribution and surface damage.