Question

A threaded bolt of major diameter is 18 mm. To make a bolt of uniform strength, a hole is drilled at center of th bolt in shank portion. Assume core diameter equals to 0.8 times of nominal diameter. What is the diameter of hole?

• A. 18.2 mm
• B. 14.4 mm
• C. 12.8 mm
• D. 10.8 mm

Answer 1

The correct option is D 10.8 mm

For uniform strength, area should be same in shank and threaded portion, we know that $d_c=0.8d$

$d_c=0.8\times 18$

= 14.4 mm

$d_1=$ Diameter o hole drilled

$\frac{\pi }{4}{d}^2-\frac{\pi }{4}{d}_1^2=\frac{\pi }{4}{d}_c^2$

$d_1=\sqrt{d^2-d_c^2}=10.8mm$