Hard Drive Platter Thicknesses

It should come as no surprise that hard drive platters have different thicknesses:

Hard Drive Platter Thickness
Hard Drive Platter Thickness

The thicker ones measure 1.25 mm, which is near enough to 50 mils to suggest they date back to the Good Old Days. The three thinner ones in the middle are 0.77 mm = 30 mil and could be slightly younger than dirt. There’s more where these came from and I expect more variation on the theme.

The beveled edges make the platters look thinner than they really are; they’re firmly clamped together with no space between them.

As nearly as I can tell, the IBM 350 Disk Storage Unit on the IBM 350 RAMAC had platters about 25 mil thick. Those were two feet in diameter, so they definitely don’t make ’em like they used to!

The thickness wouldn’t matter, except that the OpenSCAD program producing the hub & spacer tabs for the Mood Lights needs to know.