An original, shop-focused ASME Y14.5-2018-style reference for interpreting common callouts, tolerance zones, datums, modifiers and inspection intent.
Read left to right. Not every frame uses every compartment.
Example only. The exact meaning depends on the controlled feature, the drawing's stated standard/edition, and the modifiers actually shown.
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For a cylindrical feature when X and Y center deviations from basic location are already known.
True position shown here is diametrical: 2 × √(ΔX² + ΔY²). Bonus is only added when MMC/LMC is explicitly specified and the supplied sizes are valid.
The concepts most likely to change how a print is interpreted or inspected.
Concentricity and symmetry may appear on older ASME Y14.5 drawings, but their symbols/definitions were removed from Y14.5-2018. Always interpret a drawing according to the standard and edition stated in its title block or governing documentation.
Implementation: explanations, examples, diagrams and calculations on this page are original Machinist Companion content. No ASME standard text, tables or figures are embedded.
Primary public validation: NIST's 2023 Fundamentals of Geometric Dimensioning and Tolerancing presentations and NIST dimensional-metrology publications. ASME's public Y14.5 overview/course outlines are used to verify topic scope and current terminology. These public pages are reference/validation sources, not copied implementation content.
Scope: practical interpretation aid, primarily aligned to ASME Y14.5-2018 concepts. It is not the ASME standard and does not replace the drawing's governing standard, customer requirements, engineering authority or inspection procedure.