Relevant standards for check fixture design
1. The use of check fixtures is an extremely important means to achieve product inspection in ISO-GPS and AMSE-GD&T standards
2. The structure design and dimension chain tolerance allocation of the check fixture have an important impact on the product quality and the cost of the check fixture. The correct tolerance allocation of the check fixture is helpful to reduce the risk of measurement
3. The check fixtures are divided into measuring check fixtures (go gauge, no go gauge, ring gauge, block gauge) and functional check fixtures according to their functions
4. Tolerance distribution principle of checking tools: absolute tolerance method (pessimistic tolerance), optimistic tolerance method, and inclusive tolerance method
The standards related to the design of dimensional tolerance and geometric tolerance checking tools mainly include:
1. GBT1957-2006 Smooth Limit Gauge
2. GBT 10920-2008 Thread Gauges and Smooth Limit Gauges Types and Dimensions
3. GBT8069-1998 Standard for Functional Gauges
4. ASME Y14.43-2011 Dimension Specifications and Tolerance Measurement Principles for Measuring Tools and Fixtures
（Dimensioning and Tolerancing Principles for Gages and Fixtures）
Precautions for design and use of check fixtures:
1. Smooth limit gauges for measuring shaft and hole diameters GB/T1957-2006 Technical Conditions for Smooth Limit Gauges are applicable to measuring the length, width, height and depth of workpieces (linear dimension gauges), or inspecting the inner cavity and contour of workpieces (template gauges)
2. Functional gauges for parallelism, perpendicularity, inclination, coaxiality, symmetry and position of the tested elements on the inspection workpiece drawing in compliance with the relevant principles (including principle, maximum material principle) (GB/T8069-1998, ASME Y14.43-2011)
3. Both the functional gauges in GB/T8069-1998 and the check fixtures in ASME Y14.43-2011 are essentially functional check fixtures used to verify the contour and effective boundary of size and tolerance under the maximum material condition, and their purpose is to accept qualified products and reject unqualified products
4. The functional check fixture is a full shape through end check fixture. Generally, the actual dimensions of the measured elements and datum elements of the workpiece can be inspected with the functional check fixture only after they are measured and inspected as qualified.