B97.2-1970 (R2002)

1. Scope 1.1 Before an attempt can be made to measure or gauge the requirements specified on engineering drawings or specifications, to ascertain whether an actual size or value meets the specified limits, it is essential to establish a precise interpretation of the limiting values, and the standard conditions under which they shall be measured. It is the intent of this standard to provide such an interpretation of the limits, which forms the ideal toward which to strive in measuring or gauging. 1.2 In actual practice it is not possible to achieve perfect precision, because there will be deviations caused by gauge manufacturing tolerances, wear of gauges and measuring instru ments, measurement errors, and other systematic and random errors found in gauging and measuring techniques. This Standard indicates some causes of these deviations, such as environmental effects , temperature, measuring force, and surface roughness. It does not specify the extent or direction of variables associated with measurement and gauging, such as gauge tolerances and allowances, w hich are covered in standards on the principles and design of gauging. 1.3 This standard is not intended to designate areas of responsibility between supplier and customer, in determining whether or not a part is within its specified limits. 1.4 The interpretations herein are intended to be applied to all manner of numerical requirements shown on engineering drawings and specifications, such as chemical, physical and electrical requirements, as well as linear dimensions. 1.5 Limits and tolerances, when being assigned on drawings and specifications, should be made sufficiently large, within the bounds of functional requirements, to provide for ease of manufacture, and to provide for variables in gauging and measuring procedures as noted herein.