Photos show the machine work to make "Al-Fin" style replacement brake drums for an Osca MT4.
Liners are cast iron and from a Ford Thunderbird application. Outside is turned for a shrink fit into the aluminum drums. The spline assures the liners will not slip in service. 
Finished assemblies have the ID turned after the liner were installed.  Drum ID is aprox 10.180" where shrunk together. Spline has 66 teeth and the radius of each curve is .260" .