Metrology

Metrology is the science of measurementDimensional metrology is that branch of Metrology which deals with measurement of “dimensions“ of a part or workpiece (lengths, angles, etc.)Dimensional measurements at the required level of accuracy are the essential link between the designers’ intent and a delivered product.

Aspects of Metrology

Reference standard metrologyEngineering Metrology

Basic Measurement Devices

Surface PlatesTest StandsDial GagesMicrometers and VerniersGage Blocks

Dimensional Metrology Needs

Linear measurementsAngular measurementsGeometric form measurements Roundness Straightness Cylindricity Flatness, etc

Dimensional Metrology Needs

Geometric relationships Parallel, perpendicular, etc. Concentric, runout, etc.

Controlled surface texture

Communicating Dimensional Metrology Needs

Geometric Dimensioning and Tolerancing (GDT)“The language of dimensional metrology”Standard symbols, etc., on part drawings.

Specification of Linear Tolerances

Angular Specifications

Angular Tolerances

Flatness Specification

Flatness Tolerances

Straightness Specification

Straightness Tolerance

Roundness Specification

Roundness applies to every section

Roundness Tolerances

Surface Profile Without Datums

Line Profile Without Datums

Surface Profile with Datums

Profile of a line with datums is similar

Surface Profile with Datums

Cylindricity Specifications

Cylindricity Tolerances

Surface Texture Specification

Surface Texture

Perpendicularity Specification

Perpendicularity Measurements

Parallelism Specification

Parallelism Measurements

Concentricity Specification

Concentricity Tolerances

Concentricity Measurements

Concentricity Measurements

Circular Runout Specifications

Circular Runout Tolerances

Total Runout Specifications

Total Runout Tolerances

Position Specifications

Position Tolerances

Simulated Datum

Datum Selection