The correct answer is: B. Nominal diameter +1.5 mm
The diameter of a bolt hole is usually taken as the nominal diameter of the bolt plus 1.5 mm. This is because the bolt needs to fit snugly into the hole in order to create a strong joint. If the hole is too small, the bolt will not fit and the joint will be weak. If the hole is too large, the bolt will not be held in place and the joint will be loose.
The nominal diameter of a bolt is the diameter of the bolt’s shank, which is the cylindrical part of the bolt that fits into the hole. The gross diameter of a bolt is the diameter of the bolt’s head, which is the larger part of the bolt that is visible above the surface.
The following is a brief explanation of each option:
- Option A: Gross diameter of bolt. The gross diameter of a bolt is the diameter of the bolt’s head, which is the larger part of the bolt that is visible above the surface. This is not the correct answer because the diameter of a bolt hole is usually taken as the nominal diameter of the bolt plus 1.5 mm.
- Option B: Nominal diameter +1.5 mm. The nominal diameter of a bolt is the diameter of the bolt’s shank, which is the cylindrical part of the bolt that fits into the hole. This is the correct answer because the diameter of a bolt hole is usually taken as the nominal diameter of the bolt plus 1.5 mm.
- Option C: Nominal diameter +2.0 mm. This is not the correct answer because the diameter of a bolt hole is usually taken as the nominal diameter of the bolt plus 1.5 mm, not 2.0 mm.
- Option D: Nominal diameter of bolt. This is not the correct answer because the diameter of a bolt hole is usually taken as the nominal diameter of the bolt plus 1.5 mm.