: [ d_ae = d + 2 \cdot m \cdot h_aP^* ] with (h_aP^* = 0.45) for side fit (DIN 5480-1 Table 1).
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You cannot measure tooth thickness directly with a caliper. You must use measuring wires (balls) or a spline gauge. : [ d_ae = d + 2 \cdot m \cdot h_aP^* ] with (h_aP^* = 0