US Patent 7562756 Clutch drum and method for manufacturing such clutch drum

A clutch drum for a multi-plate clutch in an automatic transmission is provided at an inner periphery thereof with splines by which friction plates are engaged. Each of the splines has a tooth tip having two circumferential ends. Only one of the circumferential ends of the tooth tip has a curved surface. The splines of the clutch drum may be formed by form rolling using a tooth forming tool including a tooth root. The tooth root may have a circumferentially leading end and a circumferentially trailing end in a rotational direction, with only the circumferentially leading end having a curved surface.