An example can be on the technical drawing at the physical boundary of the shape. It is identified by a datum feature symbol within a box and datum feature triangle.

Identification contained within the box is normally shown as a capital letter.  The letter will also occur in a feature control frame relating the requirements of the feature to this datum.

The datum will be positioned on the technical drawing differently depending on the requirements and functionality of the feature or features.

For example, care must be taken as to whether an axis or surface/feature extension is the required reference.

Datum is the axis of the component	Datum is a feature extension

5 of 11

Good practice online modules

← Return to the main menu

• Dimensional
• Overview of basic design and interpretation of an engineering drawing
• An introduction to datum
• An introduction to geometric tolerancing
• An introduction to the designer's role when designing a component
• An introduction to the manufacturer's role when designing a component
• An introduction to the inspector's role when designing a component