What are hard drive platters made of?

I took apart a hard drive to start makine AP Digital Light's hard drive clock, but before I cut the slot for the light to come through, I'd like to know what the platters are made of, just in case they have something harmful in them.


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blkhawk7 years ago
The platters are made of aluminum and they are coated with a film of magnetic material (I believe that is some type of oxide). It should not be harmful but do take precautions not to aspire any fine dust. Keep us posted about your progress.
JohnA4139 months ago

This is fascinating considering that now, in 2016, we have Solid State drive. It's incredible how technology evolves.

AndyGadget7 years ago
You're talking about 3.5" drives here, but just a word of warning if anyone's thinking of playing with 2.5" laptop drives. 
I took one of these apart once and bent the platter with my fingers to find what sort of 'metal' it was made of.  It was actually made of metal coated glass and it shattered and showered me with a billion razor-sharp shards.  Apart from a few minor cuts to my fingers I was OK, but I'd have probably lost my sight if I wasn't wearing reading glasses.

mine just shattered. thats why im here.

cobeal ihagy1 year ago

I just opened up hitachi 2.5" hts725032a 320gb sata and the platters are metal like mini 3.5" drives. A few years ago I went to bend the platters in another 2.5" drive to render them useless and they were glass and exploded and a tiny shard caught my eye. So they come both ways and the glass models are dangerous to pry on.

MichaelM1 ihagy3 years ago

Hahaha! That's why I'm here

qwertyboy (author)  AndyGadget7 years ago
Wow, I had no idea that they were glass. I would have thought they were the same material as a regular hard drive.
I don't know if all the 2.5" ones are glass, but I certainly found out the hard way that the one I was bending was.
raleighr32 years ago

for future reference:

Drive platters are composed mostly of highly polished aluminium or glass with thin layers of other materials deposited on then. These materials used are to achieve the required smoothness, magnetic storage capability and lubrication.

The materials used in the layers are Ruthenium alloys, Cobalt-Nickel-Iron alloys, Cobalt-Chromium-Platinum alloys.

chooks0072 years ago

safe to say there is more than a hand full of different answers to what material the platters are made from, but for your answer any 3.5 hard drive platter would be safe to cut a slot in it.. Regardless if you do have any doubts for any project just take necessary safety measures - sectioned off designated workspace with close proximity to tap water, fire extinguishers and liquid spill kits. And safety wear (goggles, gloves, fitted clothing preferably fire resistant material).. a second person is also a good idea, not much one person can do with any issue if they were to be knocked out (ive worked with all sorts of industrial machines and every power tool and never had any accidents but i was once knocked out for a few minutes when a small dremel hobby drill caught one of my dreadlocks that fell in front of my face, wrapped up the dread pulling drill from hand and smacked me right in my temple. Had it been a lathe i may have been scalped)

TomA52 years ago

from outter-most layer to inner-most layer, the composition of a 3.5" hard drive platter is as follows...5 micron thick layer of cobalt, the magnetic data substrate. 20 micron thick layer of 90% nickel & 10% phosphorus, making the nickel non-magnetic (This layer is present because nickel takes a very high polish and cobalt (the outter-most layer) does not adhere well to the inner-most layer. The inner-most layer is comprised of 96% Aluminum & 4%Magnesium; Aluminum is cheap and lightweight, and magnesium strengthens aluminum.

I happen to work with a Niton X-Ray gun and came across a few hard drive platters at work. So I gunned them :) Heres what I found:

I igrinder the surface to get a more accurate reading, though , despite my best efforts , I may have just ground the nickel deeper into the matetial


But what about the platinum? Shouldn't it be covered with that too? http://www.ebay.com/gds/Paying-too-much-for-platinum-from-hard-drive-platters-/10000000008494913/g.html

boxfreind4 years ago
Also, I am not aware of any toxic materials inside a hard drive.....at least nothing that would pose any type of health risk. I have taken hundreds of these apart within the last 15 years without any sort of protection and I am just fine.
boxfreind4 years ago
From what I understand, they used to be made of some sort of metal coated with a magnetic layer of nikel. Now days they are made of what is basically a type of glass or ceramic (depends on manufacturer) also coated in Nikel.
Salsands5 years ago
I'll tell you one thing: putting a bare 2.5 hd platter on the surface of an iPad does not make the iPad very happy.
jheinzen6 years ago
The plates themselves are constructed with a combination of metal, glass and ceramics. They are also covered in an extra layer of thin carbon for protection, followed by a layer of magnetic material which is what is manipulated to signify data.
orksecurity7 years ago
GIFY. Typing your question directly into a websearch engine yields Wikipedia's entry as its first hit, which does answer your question.