Which dimension convention is preferred to avoid arbitrary size decisions?

• A. Nominal dimensions with standard cutting sizes
• B. Arbitrary dimensions with custom cutting sizes
• C. Nominal dimensions with custom cutting sizes
• D. Arbitrary dimensions with standard cutting sizes

Answer: (A)

Starting with a nominal size that aligns with standard stock makes size decisions predictable and efficient. By prescribing a nominal dimension and using standard cutting sizes, you reference easy-to-source stock and common machining steps, so parts are readily interchangeable and produced with less waste and fewer special tools. This approach minimizes the need to fine-tune exact finished sizes from scratch and keeps production cost and lead time down.

If you opted for arbitrary dimensions with custom cutting sizes, you’d be pushing the shop to create unique targets and tooling for each part, driving up cost and delays. Using nominal dimensions with custom cutting sizes preserves the standard reference while diverging from those standard cuts, which undermines the efficiency of using ready-made stock. Arbitrary dimensions with standard cutting sizes still forces a decision about the exact finished size, even though the raw stock is standard, which can lead to unnecessary adjustments.

Thus, the best approach is nominal dimensions paired with standard cutting sizes.