Precision Gage Blocks for Length Measurement (Through 20 in. and 500 mm)
|Publication Date:||1 January 1984|
This Standard covers specifications for gage blocks up to and including 20 in. and 500 mm in length, including physical properties, general dimensions, tolerance grades, flatness, parallelism, surface texture requirements, and definitions of length. It is not the intent of this Standard to preclude the use of other styles (shapes), classes, and types (material) of gage blocks provided they are properly correlated by the manufacturer and user to this Standard and yield comparable results with respect to conformance within specified limits.
The tolerance grade numbering system for gage blocks has replaced the letter grade designations. Tolerance grade 0.5 gage blocks (formerly grade AAA) are intended for extremely high precision work where deviations from nominal size must be a minimum. Tolerance grade 1 gage blocks (formerly grade AA) are for laboratory reference standards. They are used for calibrating other gage blocks and for high precision gaging. Tolerance grade 2 gage blocks (formerly grade A+) generally are inspection and toolroom standards. Tolerance grade 3 gage blocks (a compromise between former grades A and B) are used as shop standards.
Quality Assurance Provisions
It is expected that ANSI Standards Committee B89 will, in the near future, prepare a standard covering the inspection and measuring procedures for gage blocks. In the interim, refer to Federal Specification GGG-G-15C-1975 Gage Blocks and Accessories, for this information. However, it should be understood that the Quality Assurance Provisions specified in the Federal Specification are not specifically applicable to this Standard. It is not the intent of this Standard to limit or preclude the use of any gage block manufacturer's quality assurance system, or inspection procedures, or both, provided they insure compliance to Sections 3 through 8 of this Standard.
The Appendices describe how to specify gage blocks for specific accuracy level use, list popular gage block sizes, cover suggestions for preparing used gage blocks for recalibration, guidelines for care, use, and for periodic recalibration, and suggest when worn gage blocks should be replaced.