I dug this hard drive spindle out of a dead harddrive. Its the thing that sits right on top of the spindle with like 3 little Torox screws on it. When I got it off this thing looks shiny grey, like some grade of stainless steel but they are totally non magnetic… I mean I stuck the strong magnet from the same harddrive on it and it acted like it was nothing. The metal is hard too, a file just remove a little bit of the metal and seems to damage the file rather than the file doing anything to it. It weights very little, almost like aluminum but its NOT aluminum. The color isn’t the same (the whole harddrive spindle is aluminum and this metal is darker)
I am suspecting Titanium, what do you think?
heres a picture…
This is under a very strong magnet that also came with the harddrive. Note this thing did NOT even react to strong magnetic force.
It could be stainless steel. Some grades are very unmagnetic. The more ‘stainless’ the steel is, the less magnetic it is, due to the addition of greater amounts of non-ferrous metals like chromium, nickel etc. OTOH, the more non-ferrous metal is added the whiter the color becomes. Most titanium alloys are somewhat grey in color. That, and the light weight, leads me to believe your part is indeed titanium.
I would think that even unmagnetic stainless steel would weight half a ton, because as far as I know steel is heavy. Aluminum is very light but its easy to tell because it appears very white, they oxidize quickly, and very soft too. I know the only advantage to Titanium is they are almost as hard as steel (although some good steel is much harder) but weights only a little more than aluminum, which is very useful for aircraft application. But why would they use titanium spindle cover on a harddrive?? do they expect people to pour corrosive stuff on the thing and expect it to work?
[quote=“rahimiiii”]I would think that even unmagnetic stainless steel would weight half a ton, because as far as I know steel is heavy. [/quote]It’s the other way around. The less magnetic it is (ie, the more stainless) the heavier it will be. Yes, it’s heavy stuff, and it’s difficult to machine too. [quote]Aluminum is very light but its easy to tell because it appears very white, they oxidize quickly, and very soft too.[/quote]Basically, yes.[quote] I know the only advantage to Titanium is they are almost as hard as steel (although some good steel is much harder) but weights only a little more than aluminum, which is very useful for aircraft application. [/quote]Not necessarily. Note that pure titanium is seen as infrequently as pure aluminum, it’s almost always alloyed with other metals. Some very common titanium alloys are harder than typical grades of mild steel. It’s not how hard titanium is that makes it useful in aerospace applications, it’s its tensile strength. Titanium also ‘rusts’ btw, just very slowly.[quote]But why would they use titanium spindle cover on a harddrive?? do they expect people to pour corrosive stuff on the thing and expect it to work?[/quote]I think you nailed the other advantage in your first sentence: it’s not magnetic! 
It’s most likely a nickel alloy such as monel, inconel, hasteloy: light-weight, tough, corrosion resistant.
These materials are used for weapons/jet engine components as well.