Hard disk material

Perhaps. Some sort binder as found in enamel paints might work as well. The drum is quite low density, and does not have air bearing heads. The head heights are actually adjustable with a bunch of set screws. The heads themselves are also pretty big. This is a late 1950s drum, not a 1970s era hard disk - there is a world of difference. I would bet the heads ride a few thousands above the surface. The whole assembly is in a very rigid cast chassis, driven by a relatively low-frills AC motor, apparently. My thinking is that the drum could be recoated (this is assuming it is indeed shot), and using the rigid cast chassis, ground down to a smooth surface with a custom made tool. This is much like a "poor mans wheel lathe" used on railroad wheels. As long as the bearings are still pretty tight, there should be very little wobble between the drum and chassis. With each head being adjustable for height, much inaccuracy across the drum becomes fairly unimportant. Inaccuracy around the drum is more of an issue, but I suspect it will not be too bad if the correct tool material and magnetic coating is used, and the drum ground down gently. I will ask my real machinist friends about the tooling, as I doubt I (or any of us) could make it. -- Will