Brake Drum Hub Assembly Mystery

As mentioned, the drum was swedged onto the hub to create a single assembled unit. Not only does it make it easier to install, but final machining of the drum's inside surface was done after the hub was installed. The pressing process can, and often does, distort the friction surface. If there were any concentricity/runout issues between the hub and friction surface after pressing/swedging, they were eliminated on the brake lathe.

When replacing drums or rotors on a press-together assembly like that, the drums or rotors must be turned after assembly. Years ago, in the days of US and Canadian drum/rotor production, there was always a note to this effect in the box. A friend found this out the hard way recently after installing NOS, US-made Raybestos front drums on a non-Mopar. The note was there saying they had to be turned prior to installation, but wasn't specific about the process. It was common knowledge 40-some years ago when they were made, but now? Well, nobody asked the old guy--me--about this, and the drums got turned before the hubs were pressed. Result? The car shakes during braking. Now they have to come off and be turned again--painful to do on expensive NOS parts made of unobtainium (aftermarket drums don't exist for that particular car).

It's something to keep in mind when replacing rotors on K-H disc-brake cars as well as two-piece drums, though drums are more susceptible to this. Either way, put them on a brake lathe to check before installing.