BS ISO 4156-3:2021 pdf download – Straight cylindrical involute splines — Metric module, side fit Part 3: Inspection 7.1.2 Choice of measuring instrument The choice of measuring instrument shall be made according to the design requirements (see ISO 4156‑1). See Table 3 and Figure 2. 7.1.3 Actual size 7.1.3.1 Dimensions over and between balls The dimension over or between balls facilitates the calculation of the theoretical actual circular tooth thickness or space width at the pitch circle diameter based on the actual tooth thickness or space width where the balls contact through one normal plane. The size measured over or between balls is a true size at 2 particular gaps and in one particular plane. 7.1.3.2 Dimensions over and between pins The dimension over or between pins facilitates the calculation of the theoretical actual circular tooth thickness or space width at the pitch circle diameter based on the actual tooth thickness or space width where the pins have a line contact. 7.1.3.3 NO GO sector gauge The NO GO sector gauge is used to inspect the specified actual tolerance limit of the circular tooth thickness or space width at the minimum material condition of the part, where the gauge contacts only at the ends. 7.1.3.4 Span size over k teeth The span measurement facilitates the calculation of the theoretical actual circular tooth thickness of external splines at the pitch circle diameter based on the measurement over a block of teeth. Before using this method, suitability should be checked. 7.1.3.5 Variable sector gauge The variable sector gauge measures the actual circular tooth thickness or space width. The actual measurement is achieved using radially locking left- and right-hand flanks and comparison to a master having a known tooth thickness or space width. 7.1.4 Effective size 7.1.4.1 GO composite gauge GO composite gauges are used to check a) that the specified effective limits of tooth thickness or space width are not exceeded at the maximum material condition of the part, b) the specified form diameter of the part, thus ensuring that the required tolerances are controlled for the full involute depth, and c) the specified length of engagement, thus ensuring that the spline maximum material limit has not been exceeded. 7.1.4.2 Variable composite gauge The variable composite gauge measures the effective size of tooth thickness or space width. The actual measurement is achieved using the radially locking left- and right-hand flanks and comparison...
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