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Difficulty: MediumScrews and Threads

A technician is comparing two threaded machine bolts of the same diameter. Bolt X has 10 threads per inch (TPI) and Bolt Y has 16 TPI. If both bolts are driven into a metal block using the exact same wrench, which of the following statements correctly describes how Bolt Y compares to Bolt X?

  1. Bolt Y provides a greater mechanical advantage but advances a shorter linear distance per revolution.Answer
  2. B
    Bolt X provides a greater mechanical advantage and advances a greater linear distance per revolution.
  3. C
    Bolt Y advances a greater linear distance per revolution because it has a higher thread count.
  4. D
    Both bolts provide the same mechanical advantage, but Bolt X advances faster.

Answer

Bolt Y provides a greater mechanical advantage but advances a shorter linear distance per revolution.
The correct answer accurately reflects the physics of a screw. A higher threads-per-inch (TPI) count (16 TPI for Bolt Y vs. 10 TPI for Bolt X) means the threads are closer together. This smaller pitch results in a shorter linear distance traveled per revolution. Because the effort force is applied over the same rotational distance (using the same wrench) but results in a smaller linear output distance, the mechanical advantage is greater. You trade distance for increased force multiplication.

Step-by-Step Solution

1
Determine the relationship between threads per inch (TPI) and pitch.
Pitch is the inverse of TPI. Bolt X has a pitch of 1/10 inch, while Bolt Y has a pitch of 1/16 inch.
Pitch defines the linear distance the bolt travels in one complete revolution.
2
Compare the linear advancement of both bolts.
Since 1/16 inch is less than 1/10 inch, Bolt Y advances a shorter distance per revolution than Bolt X.
A smaller pitch means less linear travel for each rotation.
3
Evaluate the mechanical advantage based on the pitch.
Bolt Y has a greater mechanical advantage than Bolt X.
A screw is essentially an inclined plane wrapped around a cylinder. A smaller pitch is equivalent to a shallower incline, which requires less effort force to move the load, thereby providing a higher mechanical advantage.

Key Concept

Screws and Threads
Estimated Time:1m 0s
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Topics

Screws and Threads

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