Which type of bolt is designed for easy installation with a wrench and has threading only on the last inch?

• A. Machine bolt
• B. Cap bolt
• C. Carriage bolt
• D. Wood screw

Answer: (A)

The type of bolt designed for easy installation with a wrench and has threading only on the last inch is a machine bolt. Machine bolts are specifically manufactured for use in securing machinery and components where a strong fastening is required. They are typically characterized by their uniform diameter and a partially threaded design, which allows for secure fastening with the use of a wrench. The threading that extends only on the last inch enables the bolt to be installed effectively while leaving the rest of the shank smooth, facilitating more straightforward insertion into holes without requiring additional clearance for threads along the entire length.

In contrast, the other options do not possess the same characteristics. Cap bolts, while also used in machinery, usually have a rounded head and are more associated with higher torque applications but may not specifically feature the last inch threading. Carriage bolts feature a smooth, rounded head with a square section underneath that helps prevent turning when tightened, which does not align with the design for easy wrench installation. Lastly, wood screws are specifically designed for fastening wood materials, having a tapered design and spiral threads along their entire length, making them unsuitable for the described application involving easy wrench use and partial threading.