ISO R 1938 : 1971

Introduction
1 Scope
2 General rules of inspection
    2.1 Reference temperature and measuring force
    2.2 Interpretation of size limits (Taylor principle)
    2.3 Exceeding the limits
    2.4 Choice of inspection method
3 Limit gauges
    3.1 Gauge types
    3.2 Application of the Taylor principle
    3.3 Allowable deviation from the Taylor principle
    3.4 Field of utilisation of the various types of
          limit gauges
    3.5 General design features
    3.6 Materials and further details of gauges
    3.7 Definitions and inspection of gauge sizes
          3.7.1 Cylindrical plug gauges
          3.7.2 Spherical plug, disk and rod gauges
          3.7.3 Cylindrical ring gauges
          3.7.4 Gap gauges
    3.8 Method of use of gauges
          3.8.1 Gauges of holes
          3.8.2 Gauges for shafts
    3.9 Manufacturing tolerances and permissible wear of
          gauges
          3.9.1 Symbols
          3.9.2 Limit gauges
                  3.9.2.1 Positions of tolerance zones and
                            wear limits in relation to
                            workpiece limits
                  3.9.2.2 Tolerances on size of working gauges
                  3.9.2.3 Tolerances on form of working gauges
                  3.9.2.4 Adjustable gauges of sizes above
                            180 mm
          3.9.3 Reference disks for gap gauges
                  3.9.3.1 Positions of tolerance zones with
                            respect to the workpiece limits
                  3.9.3.2 Tolerances on size of reference disks
                  3.9.3.3 Tolerances on form of reference disks
                  3.9.3.4 Relation between tolerances on gap
                            gauges and their reference disks
          3.9.4 Reference ring and plug gauges for setting
                  measuring instruments
          3.9.5 Surface finish of gauges
    3.10 Settlement of disputes
          3.10.1 Inspection by the manufacturer
          3.10.2 Inspection by the purchaser
    3.11 Marking and designation of gauges
4 Indicating measuring instruments
    4.1 Definitions relating to measurements
          4.1.1 True size
          4.1.2 Error of measurement
          4.1.3 Systematic error
          4.1.4 Random error
          4.1.5 Average
          4.1.6 Standard deviation
    4.2 Types of measuring instruments
    4.3 Measuring uncertainty of the instrument
    4.4 Total measuring uncertainty
    4.5 Inspection limits
    4.6 Influence of form errors
Figures
1 Extreme errors of form of hole allowed by the recommended
    interpretation of the limits of size
2 Extreme errors of form of shaft allowed by the recommended
    interpretation of the limits of size
3 Recommended types of gauges for holes
4 Recommended types of gauges for shafts
5 Types of gauges used to check holes, in order of preference
6 Types of gauges used to check shafts, in order of preference
7 Location of points where forces counterbalancing part
    of the weight of the gauge should be applied
8 Relation between manufacturing tolerances of gap gauges
    and of reference disks
9 Tolerance zones of limit gauges and reference disks
10 Normal distribution curve of instrument readings
11 Relation between 'test limits' and the 'limits of size'
Tables
1 Manufacturing tolerances for gauges
2 Location of the gauge tolerances and the limit of maximum
    permissible gauge wear in relation to the nominal limit
    of the workpiece, for grades 6 to 16
2A Location of the gauge tolerances and the limit of maximum
    permissible gauge wear in relation to the nominal limit
    of the workpiece, for grades 6 to 16
3 Values of SM
3A Values of SM

Deals with the inspection of plain workpieces. Defines the interpretation given to the limits of dimensions for inspection, and provides essential details regarding limit gauges and indicating measuring instruments required for inspecting tolerances of the ISO system.