What are hard drive platters made of?

[Muse]

I opened up my first HD yesterday, my first, a Maxtor 220 MB that must have been new 12 years ago. I guess it was still in working order, although I hadn't had it hooked up since around 1997, I guess, maybe more. I heard that they have strong magnets in them, and wanted at them. They're pretty cool, but the platters intrigue me. There's two of them, they are real shinny and brass colored (I suppose), and they seem metallic. They make a real cool bright ringing sound when tapped. They'd make cool windchimes, if I had enough of them - I have a 420 MB, 2.7 GB and 8.4 GB which may suffer the same fate. What are the platters made of? They aren't ordinary steel (they aren't attracted by magnets). I figure maybe stainless steel? I suppose they have a magnetic coating of some kind, right?

 

[thirdlegstump]

I used to think they were pancakes. Boy was I wrong. They are saw disks.

 

[Oyeve]

Most are made of metal with a special coating that stores the data. But, I dont know if it still holds true, some used to be made of glass. How do I know? Well, one day many moons ago, I took apart a laptop HD that went bad and was bored so I was messing around with the platters and attempted to bend one thinking it was made of metal and the freaking thing shattered! 30 stitches later (five on each thumb, five on each forefinger and five on each middle finger) I decided not to do that again.

 

[imported_termite]

They are made of aluminum that is highly polished with a magnetic coating.

 

[KK]

Originally posted by: Oyeve
Most are made of metal with a special coating that stores the data. But, I dont know if it still holds true, some used to be mage of glass. How do I know? Well, one day many moons ago, I took apart a laptop HD that went bad and was bored so I was messing around with the platters and attempted to bend one thinking it was made of metal and the freaking thing shattered! 30 stitches later (five on each thumb, five on each forefinger and five on each middle finger) I decided not to do that again.

LMAO, that's a good story. Must have freaked you out after it shattered and your fingers and thumbs were dripping with blood.

 

[Muse]

Originally posted by: Oyeve
Most are made of metal with a special coating that stores the data. But, I dont know if it still holds true, some used to be made of glass. How do I know? Well, one day many moons ago, I took apart a laptop HD that went bad and was bored so I was messing around with the platters and attempted to bend one thinking it was made of metal and the freaking thing shattered! 30 stitches later (five on each thumb, five on each forefinger and five on each middle finger) I decided not to do that again.

Oh, man! Thanks for reporting that. As William Blake noted, "If others had not made mistakes before us, we would make them." That may be accurate or maybe not, but I think it gets the point across, but hardly more eloquent that what you wrote. I was wondering yesterday if they were glass or metal, and I couldn't decide for sure. I finally decided probably metal, but I wasn't sure at all. I'll sure not try to bend them with my hands!!!

 

[Muse]

Originally posted by: termite
They are made of aluminum that is highly polished with a magnetic coating.

No, Termite, they are too heavy for aluminum (I'd decided). I'd decided they are heavy enough for glass or steel, and if steel they were obviously stainless (no response to a magnet).

I see this is your first post at Anandtech Forums, and you joined today. Welcome to Anandtech!

 

[Lonyo]

Originally posted by: Muse

Originally posted by: termite
They are made of aluminum that is highly polished with a magnetic coating.

No, Termite, they are too heavy for aluminum (I'd decided). I'd decided they are heavy enough for glass or steel, and if steel they were obviously stainless (no response to a magnet).

I see this is your first post at Anandtech Forums, and you joined today. Welcome to Anandtech!

Actually, you are both right:

The platters are the disks inside the drive. Platters can vary in size. Often the size of the drive, 5.25" or 3.5", is based on the physical size of the platters. Most drives have two or more platters. The larger capacity drives have more platters. They are usually made of an aluminum alloy so that they are light. The newest and largest drives make use of a new technology of glass/ceramic platters. This is glass with enough ceramic within to resist cracking. This glass technology is taking over aluminum in the hard drive industry. Many popular manufacturers already use it, including Maxtor, Toshiba, and SeaGate. Glass platters can be made much thinner than aluminum ones, and they can better resist the heat produced in operation.

 

[lobadobadingdong]

I'd have to find my old text books, but the platters are made of several metals sandwiched together (6 different metals if memory serves me right), the outside of the hard drives are aluminum, ~ 1/8 - 1/4 inch thick

 

[Muse]

Originally posted by: lobadobadingdong
I'd have to find my old text books, but the platters are made of several metals sandwiched together (6 different metals if memory serves me right), the outside of the hard drives are aluminum, ~ 1/8 - 1/4 inch thick

Yes, I decided the outside casing was aluminum and put the casing in my AL recycling box. The platters, I decided, may indeed be glass. They have that beautiful tinkling ring very reminiscent of crystal (like in fine glassware). The particular platters that I'm now looking at are from a 12 year old 220 MB drive. I have several newer drives, though, and I wonder what I will find if and when I open them.

 

[VirtualLarry]

I thought that the outer "shell" castings of most HDs were iron/steel? Are they Al too? Older HD platters used to be Al, with some form of ferrous oxide layer coating, along with "pixie dust" or whatever additives they use nowadays. Some are glass too, IBM was one of the first to use glass platters, they are actually stronger than Al-based ones, and used more for laptops than desktops. The ill-fated IBM 75GXP used glass platters, along with ceramic (rather than steel) ball-bearings, along with a laptop-like ramp head load/unload mechanism. Quite the nice, quiet, fast, cutting-edge technology drive... well, until it failed, of course.

Btw, the chemical "bath" that they put those platters through - they use some chemicals, some of which may be carcinogenic, so I wouldn't handle them too much without gloves or something. Google "IBM fishkill lawsuit" for more info.

 

[Pariah]

Platter Substrate Materials

Glass is a new material, and would not be in a 12 year old drive. Here is what the platters you are looking at are made of (2nd page of link above):

"Older hard disks used oxide media. "Oxide" really means iron oxide--rust. Of course no high-tech company wants to say they use rust in their products, so they instead say something like "high-performance oxide media layer". :^) But in fact that's basically what oxide media is, particles of rust attached to the surface of the platter substrate using a binding agent. You can actually see this if you look at the surface of an older hard disk platter: it has the characteristic light brown color. This type of media is similar to what is used in audio cassette tape (which has a similar color.)"

 

[Oyeve]

Originally posted by: Pariah
Platter Substrate Materials

Glass is a new material, and would not be in a 12 year old drive. Here is what the platters you are looking at are made of (2nd page of link above):



I sliced my finger on a laptop HD about 6 years ago, so it's not relatively new. Maybe at the time glass was primarily used for laptop HDs because they run cooler.

 

[thorin]

I can vouch for the fact that modern HD platters are glass, I've shattered a few of them over the past few years.

Thorin

 

[Muse]

Originally posted by: thorin
I can vouch for the fact that modern HD platters are glass, I've shattered a few of them over the past few years.

Thorin

I'm thinking now that mine is metal. I was washing one (in case there are carcinogens on it, as hinted in a post above, eek!) and dropped it in the sink. Made loud noise, but didn't break. Yes, I could make a more rigorous test with a hammer or throwing down on concrete, but I'm thinking stainless steel for this 12 year old HD. It's way too heavy for aluminum. The coating is very very likely iron oxide. Very pretty. I'm going to take apart 2 or 3 of my other HDs and make wind chimes out of the platters! I figure them all for metal. I'll make refrigerator magnets out of the magnets (glue to wood).

 

[Pariah]

Originally posted by: Oyeve

Originally posted by: Pariah
Platter Substrate Materials

Glass is a new material, and would not be in a 12 year old drive. Here is what the platters you are looking at are made of (2nd page of link above):



I sliced my finger on a laptop HD about 6 years ago, so it's not relatively new. Maybe at the time glass was primarily used for laptop HDs because they run cooler.

Might want to look up what the word relatively means.

 

[thorin]

If it's 12 years old then it's not glass.

Thorin

 

[farmercal]

I personally took apart a bunch of hard drives here at work for destruction purposes (regulations). The desktop platters (not new hard drives but not that old), are made from a shiny silver metal with a mirror finish. I know that they are metal because I bent them very much and when you drop them on a counter they give a metallic ring. The metal DOES NOT adhere to a strong magnet what-so-ever, so I figure they have to be made of an aluminum alloy that is coated with something that makes is store the data. Out of all of the laptop drives I dismantled for destruction, all were glass and much easier to destroy.