The drawing and the material certificate are contracts. These standards define how to read them, which is why a part can be accurate and still be rejected, and why the right machine depends on what the drawing actually demands.
U.S. drawings usually invoke ASME Y14.5; many European and Asian drawings invoke the ISO GPS (Geometrical Product Specifications) system. The symbols look similar, but default rules differ. Check the title block before you quote, program or inspect.
Issued by ASME
The U.S. standard for geometric dimensioning and tolerancing (GD&T): datums, feature control frames, form, orientation, location, profile and runout tolerances, and the rules that govern them.
Programming, fixturing and inspection all follow the datum scheme. Misreading it is a classic cause of rejected first articles.
Machine capability claims mean more when tied to the tolerances buyers actually hold: true position, profile and runout, not just linear accuracy.
Tight geometric tolerances on large parts are where machine geometry (ISO 230-1) and thermal stability matter most.
Status (reviewed October 7, 2026): ASME Y14.5-2018 is the current edition.
Source: ASME codes and standards ↗
Issued by ISO (TC 213)
The international system for geometric tolerancing and its fundamental rules. ISO 8015 sets principles such as independency as the default; ISO 1101 defines geometric tolerancing.
Why it matters: Same-looking symbols can carry different defaults than ASME Y14.5. Quote and inspect to the system the drawing invokes.
Source: ISO Online Browsing Platform ↗
Issued by ISO
General tolerances apply to dimensions without an individual tolerance. ISO 2768-1 covers linear and angular dimensions in classes (f, m, c, v). General geometrical tolerances, formerly in ISO 2768-2, are now addressed in the GPS system by ISO 22081 (2021).
Why it matters: “ISO 2768-mK” in a title block quietly sets the tolerance for most dimensions on the drawing; ignore it and good-looking parts fail inspection.
Source: ISO Online Browsing Platform ↗
Issued by ASME · ISO
Define surface texture parameters such as Ra and Rz, and how to measure them. In the ISO system, the ISO 21920 series (2021) replaced the older profile standards ISO 4287 and ISO 4288.
Why it matters: Finish requirements drive spindle condition, tooling, machine damping and the final operation. An Ra callout on an implant or sealing face is a functional requirement.
Source: ASME codes and standards ↗ ISO Online Browsing Platform ↗
Issued by ASME · ISO
ASME B1.1 defines Unified inch screw threads (UNC, UNF and classes such as 2B/3A); ISO standards define general-purpose metric threads, their tolerances and gauging. Aerospace and medical drawings often call up additional thread specifications.
Why it matters: Thread class and gauging method decide acceptance. Thread milling, rigid tapping and single-point capability are machine selection questions.
Source: ASME codes and standards ↗
Issued by ASTM International (formerly the American Society for Testing and Materials)
Develops more than twelve thousand standards for materials, products and test methods, from steel and aluminum product specifications to hardness and tensile testing and medical implant materials.
Why it matters: Material specifications define what you are allowed to buy and what the certification must show. Test methods (hardness, tensile) define how properties are proven.
Source: ASTM International ↗
Issued by CEN (European Committee for Standardization)
Defines the types of material certificates: 2.1 and 2.2 (declarations by the manufacturer), 3.1 (inspection certificate with specific test results, validated by the manufacturer’s independent inspection representative) and 3.2 (validated additionally by the purchaser’s or a third-party inspector).
Aerospace, medical, energy and defense work typically require 3.1 or better, traceable by heat number to the material on the shelf.
Surplus material with matching 3.1 certs is worth far more than the same bar without paperwork.
Match heat numbers on the cert to the material; a cert that cannot be tied to the bar proves nothing.
Source: CEN ↗
Issued by ISO (TC 213)
How CMM and other coordinate measuring systems are tested for length measurement error, probing error and related performance, so their specifications can be verified on delivery and periodically after.
Your inspection capability is part of your process capability; a CMM out of verification undermines every report it produces.
A recent ISO 10360 reverification report makes a used CMM sellable to quality-minded buyers.
Compare CMM specifications only when stated to the same ISO 10360 part and conditions.
Source: ISO Online Browsing Platform ↗
Machine Blue Book does not sell certification, consulting or machines, and is not affiliated with any standards body named here. Standards are copyrighted by their publishers; this reference describes them in our own words and links to the issuing organization. It is educational, not legal or regulatory advice. Facts reviewed October 7, 2026. Found an error or a change? Tell the editor.
