A production drawing for a large industrial frame shows a dimension of 1800 mm (70.87 in.) with a tolerance of ±2 mm (±0.08 in.). The drawing also includes a general note specifying 'All dimensions are in millimetres unless otherwise stated, and general tolerances are ±1 mm (±0.04 in.).' How should a welder interpret the acceptable range for the 1800 mm dimension?

Question: A production drawing for a large industrial frame shows a dimension of 1800 mm (70.87 in.) with a tolerance of ±2 mm (±0.08 in.). The drawing also includes a general note specifying 'All dimensions are in millimetres unless otherwise stated, and general tolerances are ±1 mm (±0.04 in.).' How should a welder interpret the acceptable range for the 1800 mm dimension?

Answer options:

• The dimension must be precisely 1800 mm (70.87 in.) due to the tight tolerance.
• The range is 1799 mm to 1801 mm (70.83 in. to 70.91 in.) based on the general tolerance. ✅ The range is 1798 mm to 1802 mm (70.79 in. to 70.94 in.) based on the specific tolerance.
• The range is 1797 mm to 1803 mm (70.75 in. to 70.98 in.) due to cumulative tolerances.

Correct answer: The range is 1798 mm to 1802 mm (70.79 in. to 70.94 in.) based on the specific tolerance.

Explanation: Specific tolerances indicated directly with a dimension on a drawing override any general tolerances listed in a notes section. Therefore, the acceptable range is 1800 mm ± 2 mm, which means from 1798 mm to 1802 mm. General notes apply only when no specific tolerance is given for a particular dimension.