Through how many thimble rotations must a standard micrometer be turned to make the spindle move exactly 1/4 inch?

To understand how many thimble rotations are needed for a standard micrometer to move the spindle exactly 1/4 inch, it's important to grasp how micrometers function. A standard micrometer typically has a pitch of 40 threads per inch on the screw. This means that for every complete turn of the thimble, the spindle moves 1/40 of an inch.

To find out how many rotations are necessary to achieve a movement of 1/4 inch, or 0.25 inches, the following calculation can be performed:

1. Determine how many increments of 1/40 are needed to reach 1/4 inch:

[

\frac{1/4 \text{ inch}}{1/40 \text{ inch per rotation}} = \frac{1/4}{1/40} = \frac{40}{4} = 10

]

This calculation shows that 10 complete thimble rotations are required to cause the spindle to move 1/4 inch. Thus, the correct answer is ten rotations. Understanding the pitch of the micrometer and how much it translates into linear movement is crucial for accurately determining the number of turns needed for various measurements, which is