Ensure Design Accuracy, Manufacturing Efficiency, and Global Compliance.
Why us ?
At Petra Tech, we specialize in applying GD&T (Geometric Dimensioning and Tolerancing) and rigorous standardisation practices aligned with ISO and ASME Y14.5 standards. Our expertise guarantees that your engineering drawings are not only clear and unambiguous, but also fully compliant with international standards — reducing manufacturing errors, streamlining inspection, and improving cross-team communication. Whether you’re optimizing existing designs or starting from scratch, our services bring precision, consistency, and confidence to every stage of your product lifecycle.
What are ISO GD&T standards?
The ISO GD&T standards are a collection of international standards published by the International Organization for Standardization (ISO) that define how Geometric Dimensioning and Tolerancing (GD&T) is applied to engineering drawings and 3D models. These standards ensure consistency, clarity, and global compatibility in how geometry, tolerances, and functional requirements are communicated.
Core ISO GD&T Standards
ISO 1101
Geometrical Product Specifications (GPS): Geometrical tolerancing – Tolerances of form, orientation, location and run-out.
ISO 5458
Geometrical tolerancing - Positional tolerancing:
Deals with how position tolerances should be applied.
ISO 14405 (PARTS 1-3)
ISO 5459
Datums and datum systems:
Defines how to establish and interpret datum features and datum systems.
ISO 8015
Fundamentals of GPS - Concepts, principles and rules:
Defines default rules like independency principle, unless otherwise specified.
Covers size and distance dimensions (linear, angular, etc.)
Supporting and Related Standards
ISO 2692
Maximum material requirement (MMR), Least material requirement (LMR), and Reciprocity​
ISO 1660
Projecting tolerance zones and coaxiality
ISO 10578
Profile tolerances
ISO 18391
Free state condition and restrained condition
ASME Y14.5
LATEST UPDATE : -2018
What it covers ?
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1. GD&T Symbols and Definitions
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Flatness, straightness, circularity, cylindricity
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Perpendicularity, parallelism, angularity
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Position, concentricity, symmetry
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Circular and total runout
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Profile of a surface/profile of a line
2. Feature Control Frames
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How to communicate tolerances using standard symbols and modifiers
3. Datum Systems
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How to select and structure datums (A, B, C, etc.)
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Rules for datum referencing, mobility, and simulators
4. Tolerance Modifiers
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MMC (Maximum Material Condition), LMC, RFS
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Projected tolerance zones, tangent plane, free state, etc.
5. Tolerance Zones and Interpretation
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Rules for how tolerance zones are shaped, oriented, and related to features
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Boundaries, limits, and interpretations under worst-case scenarios
6. Tolerance Accumulation (Implied Relationships)
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Virtual condition boundaries
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How tolerances accumulate across assemblies
7. Drawing Rules and Practices
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Basic dimensions
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Feature-of-size rules
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Inspection planning and default assumptionsS
