Old national standard GB 4987-85 (obsolete): Clearly divided into four grades: 000, 00, 0, and 1. Grade 000 is the highest. Formula:
Grade 000 flatness: (1 \\times (1 d\/1000) \\mu m)
Grade 00: (2 \\times (1 d\/1000) \\mu m)
d = diagonal in mm, at 20\u00b0C (Douyin Baike).
Replacement new version GB\/T 20428-2006 \/ 2021: Removed Grade 000; the official grades are only: 00, 0, 1, and 2.
Verification procedure JJG117-2013 (Verification of Flatness of Surface Plates): The procedure only goes up to Grade 00, with no verification criteria for Grade 000.
\ud83d\udc49 In other words: Third-party metrology institutes cannot issue a “Grade 000” verification certificate; at most, they can verify it to Grade 00, and the report will only state the actual measured flatness value.<\/li>\n\n\n\n
It means achieving the flatness tolerance of Grade 000 from the old GB4987-85 (the k=1 tier);
Widely used for metrology bases, CMM bases, semiconductors, and optical bases;
It must be in a strictly constant temperature environment of 20\u00b10.5\u00b0C with vibration isolation; ordinary workshops cannot achieve Grade 000 performance at all.<\/li>\n<\/ol>\n\n\n\n
Example: A 1000\u00d71000 plate, diagonal \u2248 1414mm
Industry colloquial Grade 000 tolerance: \u2248 2.4 \u03bcm
National standard official Grade 00 tolerance: \u2248 4.8 \u03bcm<\/p>\n\n\n\n
- \n
- Critical pitfalls in procurement and contract signing (Practical focus)
Do not just write “Grade 000”, as metrology agencies do not recognize this grade name;
Write the flatness tolerance value the referenced calculation formula directly in the contract \/ technical agreement, for example:
Working surface diagonal d, flatness \u2264 (1 \\times (1 d\/1000) \\mu m) (at 20\u00b0C);
Third-party certificates will only print the actual measured flatness in \u03bcm, not the words “Grade 000”;
Many small factories falsely label products as Grade 000, while actually only achieving Grade 00 or even Grade 0, because there is no mandatory standard constraint.<\/li>\n\n\n\n - \u041a\u0440\u0430\u0442\u043a\u043e\u0435 \u0438\u0437\u043b\u043e\u0436\u0435\u043d\u0438\u0435
\u2705 This industry term exists, originating from the abolished old national standard GB4987-85;
\u274c Current national standards and national verification procedures do not have “Grade 000” as a legally defined accuracy grade;
\u2705 Products can achieve the flatness indicators corresponding to Grade 000, but the certificate will not be labeled “Grade 000”.<\/li>\n<\/ol>\n\n\n\n![\"\"](\"https:\/\/jtlcnc.com\/wp-content\/uploads\/2026\/08\/q-1-1024x544.png\")
<\/figure>","protected":false},"excerpt":{"rendered":"\u0421\u0443\u0449\u0435\u0441\u0442\u0432\u0443\u0435\u0442 \u043b\u0438 \u043a\u043b\u0430\u0441\u0441 000 \u0434\u043b\u044f \u0433\u0440\u0430\u043d\u0438\u0442\u043d\u044b\u0445 \u043f\u043b\u043e\u0441\u043a\u0438\u0445 \u043f\u043b\u0438\u0442? \u041e\u0441\u043d\u043e\u0432\u043d\u043e\u0439 \u0432\u044b\u0432\u043e\u0434: \u0432 \u0434\u0435\u0439\u0441\u0442\u0432\u0443\u044e\u0449\u0435\u043c \u043d\u0430\u0446\u0438\u043e\u043d\u0430\u043b\u044c\u043d\u043e\u043c \u0441\u0442\u0430\u043d\u0434\u0430\u0440\u0442\u0435 GB\/T 20428-2021 \u201c\u041f\u043b\u043e\u0441\u043a\u043e\u0441\u0442\u043d\u043e\u0441\u0442\u044c \u043a\u0430\u043c\u0435\u043d\u043d\u044b\u0445 \u043f\u043b\u0438\u0442\u201d \u043a\u043b\u0430\u0441\u0441 000 \u043e\u0442\u0441\u0443\u0442\u0441\u0442\u0432\u0443\u0435\u0442; \u0432 \u043d\u0451\u043c \u043e\u043f\u0440\u0435\u0434\u0435\u043b\u0435\u043d\u044b \u0442\u043e\u043b\u044c\u043a\u043e \u043a\u043b\u0430\u0441\u0441\u044b 00, 0, 1 \u0438 2.\u0412 \u0441\u0442\u0430\u0440\u043e\u043c \u043d\u0430\u0446\u0438\u043e\u043d\u0430\u043b\u044c\u043d\u043e\u043c \u0441\u0442\u0430\u043d\u0434\u0430\u0440\u0442\u0435 GB 4987-85 \u0434\u0435\u0439\u0441\u0442\u0432\u0438\u0442\u0435\u043b\u044c\u043d\u043e \u0441\u0443\u0449\u0435\u0441\u0442\u0432\u043e\u0432\u0430\u043b \u043a\u043b\u0430\u0441\u0441 000, \u043a\u043e\u0442\u043e\u0440\u044b\u0439 \u0432 \u043d\u0430\u0441\u0442\u043e\u044f\u0449\u0435\u0435 \u0432\u0440\u0435\u043c\u044f \u043e\u0442\u043c\u0435\u043d\u0435\u043d, \u043e\u0434\u043d\u0430\u043a\u043e \u043e\u0442\u0440\u0430\u0441\u043b\u044c, \u043f\u0440\u043e\u0438\u0437\u0432\u043e\u0434\u0438\u0442\u0435\u043b\u0438 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