Jis B 7420 Pdf !!top!!

JIS B 7420:1997 is the Japanese Industrial Standard for Plain Limit Gauges

• Grade 0 (Inspection Grade): The highest precision, used in laboratories and final inspection.
• Grade 1 (Toolroom Grade): General purpose inspection.
• Grade 2 (Shop Grade): For production environments.

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1. Definitions and Symbols: Clear definitions of terms like "Go side," "No-Go side," "wear limit," and the symbols used for tolerance zones (e.g., Z, ZZ, ZT).
2. Tolerance Grades: The standard divides gauges into classes (typically Class 0, Class 1, and Class 2) depending on the precision required. Class 0 is for high-precision reference gauges, while Class 2 is for workshop gauges.
3. Dimensional Tables: Extensive tables listing the allowable deviations for each nominal diameter.
4. Wear Allowance: Unlike some other national standards, JIS B 7420 provides specific guidance on how much a "Go" plug gauge can wear before it must be replaced.
5. Material and Hardness Specifications: While not exhaustive, the standard references the necessary hardness (typically above 750 HV) and material stability for steel gauges.
6. Marking Requirements: How a compliant gauge should be marked (size, class, manufacturer, Go/No-Go identification).