I had a collection of hard drive platters piling up. Who doesn't? Each one is a highly polished aluminum mirror. I thought that there must be a 3D printed use for them. So I fired up 123D Design and made 2 different drink coaster/display bases. One based on a cylinder, with straight walls, and the other based on a torus, with curved walls.Liberate a few hard drive platters from some obsolete or defective 3.5 inch hard drives. You'll need some very small Torx bits. Look under the labels for hidden screws.All the platters seem to be the same 95mm in diameter. Some are slightly thicker than others but that doesn't matter here. The 2 designs should allow the platter to snap in place with a small bit of room for printer variations. If you find them too tight or loose, play with the X and Y dimensions in your slicer a bit. Multiply by 1.005 and see where that takes it. Be sure to multiply both X and  Y by the same amount or you'll end up with an oval that won't fit anything. Don't ask me how I know this. If using for a drink coaster, I'd recommend spreading a small layer of silicone around the edges of the interior before you put the platter in place. Leave the center of the base clear of silicone so it doesn't show.That should keep liquid from migrating under the platter.I started out printing them all black, then experimented with changing the filament color about halfway through the print. At .3mm layer height, there were 22 layers, so I changed at layer 11 or 12.I printed them with .3mm layer height in PLA at 50mm speed with 15% infill.