Metrology Metrology is the science of measurement Dimensional 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 metrology Engineering Metrology

Basic Measurement Devices Surface Plates Test Stands Dial Gages Micrometers and Verniers Gage Blocks

Dimensional Metrology Needs Linear measurements Angular measurements Geometric 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

Circular Runout Specifications

Circular Runout Tolerances

Total Runout Specifications

Total Runout Tolerances

Position Specifications

Position Tolerances

Simulated Datum

Datum Selection