Geometric Dimensioning and Tolerancing (GD&T)
Understand how GD&T communicates allowable geometric variation using datums, feature-control frames and standardized controls for form, orientation, location and runout.
Work context
Design definition and inspection
This page shows technical knowledge coverage. Course, assessment and credential availability depends on the applicable Industrial Skillset program.
Relevant roles
Machinists · Quality inspectors · Manufacturing engineers · Design engineers
Prerequisites
Engineering drawings · Dimensional measurement
Knowledge level
Intermediate coverage with practical workplace context.
Learning outcomes
What this topic is intended to help you understand
- Identify datums and feature-control frames.
- Differentiate size tolerances from geometric tolerances.
- Recognize how GD&T affects setup, measurement strategy and functional acceptance.
Technical scope
Equipment, processes and terminology
- Datums
- Feature control frames
- Flatness
- Straightness
- Parallelism
- Perpendicularity
- Position
- Profile
- Runout
- Material condition modifiers
Workplace practice
How the subject connects to industrial work
- Reading a control frame
- Establishing datum reference order
- Selecting measurement approach
- Connecting tolerance to functional intent
Quality and safety
Controls that protect people, product and process
- Inspection-method suitability
- Measurement uncertainty
- Avoiding interpretation from drawing appearance alone
Technical learning supports understanding. Actual work remains governed by site procedures, machine-specific instructions, engineering requirements, supervision and authorization.
Industrial documents
Documents commonly connected to this subject
- Engineering drawing
- Inspection plan
- CMM program
- FAI record