The right-size spline will give the life required ... of Figure 4 and from the critical speed chart of Figure 5 differ, then choose the one of larger shaft diameter. Ball splines are efficient.

“In practice, the roughing splines include grinding allowances that usually vary by the amount A=0.1 – 0.15 mm (0.004-0.006 inch), so there is no influence on other theoretical elements of the spline ...