How much radial clearance does a close fit hold for a 1/4 inch bolt?

• A. 0.250"
• B. 0.257"
• C. 0.266"
• D. 0.0035"

Answer: (D)

Radial clearance is the small gap around a shaft or bolt when it sits in a hole, and it’s measured as half of the difference between the bore diameter and the shaft diameter. For a close fit with a 1/4 inch bolt, the bore must be only slightly larger than 0.250 inches. If the desired radial clearance is 0.0035 inches, the bore diameter would be 0.250 + 2×0.0035 = 0.257 inches. So the amount of radial clearance itself is 0.0035 inches. The other numbers would correspond to either the bore size (0.250" or 0.257") or a larger clearance (0.266" would imply a larger radial gap), but they’re not the radial clearance value.