BetaBetaBetaWorks out a DIN 5480 involute spline from its reference diameter and module: its teeth, profile shift, and the shaft's and the hub's tip and root diameters.
Both inputs are in millimetres, as the standard names them; the sizes come back in unit.
Example: 25 by 1.25 -> 18 teeth, shaft tips 24.75 across, hub tips 22.5
The reference diameter, the module and the unit
The spline's sizes in unit
The sizes of DIN 5480 involute splines, with no CAD kernel needed, in the unit asked for.
occt.parts.mechanical.machining.dinbuilds a splined shaft and cuts the hub to fit it.