This reference sheet gives engineers a practical framework for designing datums that align with real machining constraints and process realities. It explains how to choose stable, accessible reference surfaces, structure datum schemes that follow natural machining order, and avoid geometric features that complicate fixturing.

Learn how to identify early‑stage datum surfaces such as planar faces and clamp‑pad bosses, along with clear warnings about thin ribs and late‑stage geometry that undermine setup repeatability. It also covers how cutter access, clamping forces, and material behavior impact the reliability of your DRF, plus when to add sacrificial tabs, bosses, or datum pads to stabilize machining.

Lastly, learn about best‑practice tolerancing rules and a checklist for collaborating with machinists to reduce setup count and variation, giving OEM engineers a way to design parts that machine, inspect, and scale with greater confidence.