Interactive GD&T Quick Reference — ASME Y14.5 Symbols Explained

How It Works

1. Browse or Click a Symbol

   Use category filters (Form, Profile, Orientation, Location, Runout) or click any symbol in the grid.

2. Read Plain-English Explanation

   Each symbol has a one-sentence definition followed by detailed explanation — no jargon.

3. Review Feature Control Frame

   See correct FCF format with tolerance value, material condition modifiers, and datum references.

4. Check Datum Requirements

   See whether datums are required (Location/Orientation) or not applicable (Form).

5. See Inspection Method

   Each symbol includes typical measurement method: indicator, CMM, surface plate, etc.

Built For

• Machinists interpreting GD&T callouts on drawings before setup
• CMM operators selecting correct measurement routines
• Quality inspectors verifying datum features before measuring
• Manufacturing engineers adding GD&T to process sheets
• Designers checking correct symbol usage and datum schemes
• Students learning geometric dimensioning and tolerancing

Features & Capabilities

All 12 Active + 2 Legacy Symbols

Complete ASME Y14.5-2018 coverage: Straightness, Flatness, Circularity, Cylindricity, Profile of Line/Surface, Angularity, Perpendicularity, Parallelism, Position, Circular/Total Runout. Plus legacy symbols Concentricity and Symmetry (removed in Y14.5-2018, still found on older drawings).

Interactive Symbol Grid

Visual grid organized by category with click-to-expand detail panels.

FCF Anatomy Diagram

Interactive feature control frame diagram showing each compartment's function.

Material Condition Modifiers

MMC, LMC, and RFS reference with practical examples of when each applies.

Inspection Methods

Standard verification method for each symbol: surface plate, CMM, V-blocks, gauge pins, etc.

PDF Export

Export as branded PDF for inspection area posting or training materials.

Assumptions

• Symbol definitions and datum requirements per ASME Y14.5-2018 (current edition of the American GD&T standard)
• Feature control frame structure follows standard compartment order: symbol, tolerance zone, material condition modifier, datum references
• Material condition modifiers (MMC, LMC, RFS) applied per Rule #2 of ASME Y14.5-2018
• Inspection methods listed are typical CMM and surface plate methods; equivalent verification is permitted per the standard
• Legacy symbols (Concentricity, Symmetry) documented per ASME Y14.5-2009 for reference on older drawings
• Datum feature simulator hierarchy follows primary-secondary-tertiary degrees of freedom convention

Limitations

• Does not cover composite tolerancing, projected tolerance zones, or unequally disposed tolerance zones in full detail
• ISO GPS system (ISO 1101) differs from ASME Y14.5 in several areas; this reference covers ASME only
• Not a substitute for formal GD&T training per ASME Y14.5-2018 or ETI (GD&T Professional) certification
• Does not include worked examples of tolerance stack-up analysis or statistical tolerance methods
• Datum reference frame establishment for complex or partial datum features is beyond the scope of this quick reference
• Profile tolerance with simultaneous requirements and composite position concepts require in-depth study beyond this reference

References

• ASME Y14.5-2018 - Dimensioning and Tolerancing (current edition of the American GD&T standard)
• ASME Y14.5-2009 - Dimensioning and Tolerancing (previous edition, includes Concentricity and Symmetry)
• ASME Y14.5.1 - Mathematical Definition of Dimensioning and Tolerancing Principles
• ASME Y14.43 - Dimensioning and Tolerancing Principles for Gages and Fixtures
• ISO 1101 - Geometrical Product Specifications — Geometrical Tolerancing (international equivalent)
• ETI (Effective Training Inc.) - Fundamentals of GD&T (widely used training curriculum reference)

Frequently Asked Questions