The inside dimension of 3/4 in 0.072 5052-0 aluminum alloy tubing is 0.606 inch. Which of the following is true about this measurement?

• A. The inside diameter is 0.606 inch
• B. The outside diameter is 0.606 inch
• C. The inside diameter is 0.500 inch
• D. The outside diameter is 0.700 inch

Answer: (A)

In tube sizing, the inside diameter is the distance across the hollow interior, while the outside diameter is the full outer width. For a tube described as 3/4 in with a wall thickness of 0.072 in, the outside diameter is 0.750 in. The inside diameter is found by subtracting twice the wall thickness: 0.750 − 2 × 0.072 = 0.606 in. So the statement that the inside diameter is 0.606 inch is correct. The outside diameter is not 0.606 (it's 0.750), the inside diameter is not 0.500, and the outside diameter is not 0.700.