A D-size drill is .004 inch smaller than a 1/4-inch fractional size. What is the decimal equivalent size of a D-drill?

To determine the decimal equivalent size of a D-size drill, we start with the fractional size, which is 1/4 inch. The decimal equivalent of 1/4 inch is 0.2500 inches.

Since the question states that a D-size drill is .004 inches smaller than 1/4 inch, we subtract 0.004 from the decimal equivalent of 1/4 inch:

0.2500 - 0.004 = 0.2460 inches.

This means the decimal equivalent size of a D-drill is 0.2460 inches. Understanding how to convert fractional sizes into decimal form and accurately performing the subtraction is crucial in determining the size of drill bits used in various applications.