Introduction: Hard Drive Sander

Many people have an old hard drive laying around. In this project we will put it to good use by turning it into a powerful disk sander! It's a cheap and easy project, but it has already proven to be very useful when sharpening tools and sanding though materials.

Let's get building!

Step 1: Parts & Tools

Parts

  • Old harddrive (although a new one would also work :p)
  • Electronic Speed Controller (about $4)
  • Servo tester (about $1.5)
  • Sandpaper
  • 2 Banana terminals

Total cost: less than $10!

Tools

  • Torx screwdrivers
  • Soldering iron
  • Dremel / rotary tool
  • Drill
  • Multimeter

WARNING

Make sure your harddrive has aluminium platters, and not glass ones. The glass platter might shatter and cause serious damage! How to check this?

  • Take a strong neodymium magnet and go over the platter. You should feel some resistance if it's an aluminium one (due to eddy currents)
  • Look at the sun though the harddrive. If you can slightly see the sun, it's glass.
  • To be completely sure: hold it in a vice, wear safety equipment (especially safety glasses!) and give it a slight hit with a hammer. If it shatters you shouldn't (and can't at this point :p) use it.

Step 2: Disassembly

The first step of the build is disassembling the harddrive. Simply remove all the screws; there will probably be one under the sticker as well.

Next, we'll need to take out the guts. Undo all the screws you see and remove the components.
You might have to use some force to remove the magnets, but these are worth keeping!

Also remove the hard drives and spacers themselves, since we'll have to restack them.

Small bonus project

These strong magnets are ideal to make a magnetic parts tray. You can remove the protruding metal bits with a pair of pliers. They will break off quite easily, since they are quite brittle.

I had a lid of an old metal pen case, to which I attached the magnets; et voila!

Step 3: Wiring the Motor

The crucial step of this project is controlling the motor of the harddrive.

The motor inside a harddrive is a brushless DC motor (BLDC). They come in 2 variants: triangle and star topology. For the full explanation, take a look at the Wikipedia page, I will focus on the wiring.

A BLDC motor can easily be controlled by an Electronic Speed Controller (ESC), and while we could have made this ourselves, it's far easier and cheaper to buy a speed controller. Furthermore, they can easily be controlled by a servo tester; as the name implies, it is used to test servo motors. However, the type of control signal for a ESC and a servo are the same: it's a simple PWM signal. In case of the servo, this corresponds to a motor position; for the ESC it corresponds to a speed.

Let's focus on the wiring of the motor, depending on your harddrive you will have 1 of 2 types:

3 Pins

If your motor has 3 pins, it's triangle topology: there is a coil between every pair of pins. This is the easy case: just solder the 3 wires of the ESC (the blue ones) to the 3 pins of the motor (a,b,c on the diagram) and call it a day.

4 Pins

In case there are 4 pins on the motor, you have a star topology. We will need to connect the ESC to points a,b,c on the diagram. To do this, we have to identify to which 3 of the 4 pins they correspond.
To achieve this, we'll have to bust out the multimeter and measure the resistance between the pins. As we can see on the picture, 3 combinations give a resistance of 1 Ohm, while 3 others give 2 Ohms. 1 Ohm is the resistance of 1 coil (1 of the Z's on the diagram), while the 2 Ohms is the resistance of 2 coils in series.
Conclusion: the combinations where we measured 2 Ohms are the ones we need (a,b,c on the diagram)!

After soldering the ESC, mount it inside the hard drive case where the reading head was. Every harddrive is different, so try to find a way of attaching it securely; I just some scraps of aluminium, although glue would have also worked.

Attach 2 banana terminals to the red an black wires of the ESC. Drill 2 holes in the enclosure to mount them. You could also use a barrel jack if you want to use it with a 12 V wall adapter instead of a bench powersupply.

You can already connect the servo tester to the 3 pin connector of the ESC, plug the banana jacks into 12 V and give the motor a try. That's the electronics basically done!

Step 4: Enclosure

Now that our motor spins, we can turn it into a sander!

Start by taking a piece of sandpaper and cut out a circle that fits your hard drive platter. Attach it to the platter with double sided tape. This will allow us to easily replace it in the future.

My harddrive had 2 platters with some spacers in between. Put the spacers down first and then add the 2 platters on top of each other for extra strength. Screw it tightly in place, this bracket will also keep the sandpaper firmly in place (that's why we didn't glue the sandpaper).

The last thing is to cover up and protect the ESC and to make it more usable. Therefore, we will reinstall the original lid, with a cutout for the harddisk. Since the cover is very hard and reasonably thick steel, it is preferable to use a thin cutoff wheel on your rotary tool. Wear some kind of face protection and a breathing mask while doing this: it produces dust and the cutoff wheel can easily break and fly away!
I also added an upright piece out of thin aluminium that seals off the side and glued it in place.

As a last step, attach the servo tester to the 3 pin connector of the ESC. I decided to leave it external, since there was not enough place inside the enclosure, and since it allows me to use it to test actual servo's when I'm not sanding.

Step 5: Test & Enjoy

We're done! The only thing left to do is to test our new hard drive sander.
Connect the servo tester and plug it into a 12 V supply which can deliver about 1 A (see how I made one from an old ATX powersupply here, or a fancy digital one here). Make sure the servo tester is in manual mode and turn the knob, the sander should start spinning!

I hope you liked the project and have found a good use for that unused old hard drive!

Feel free to check out my other instructables: https://www.instructables.com/member/ThomasVDD/

Comments

author
DanR186 made it! (author)2017-07-24

Made it for a woodworking friend. I fit all of the components inside the drive, and used the Molex connector on the circuit board to power the 12V/ground. It will run off an ATX power supply!

HD Sander.jpg
author
ThomasVDD (author)DanR1862017-07-26

Very nice! Unfortunately the inside of my HDD didn't allow me to fit everything inside, yours look very slick :)

author
schuimpge (author)2017-06-15

Hello Thomas, Good to see you really make an effort to maintain and update your instructable, especially for safety issues. I'll vote for that part, but also for the elegance of using an esc instead of just leaving the PCBA to handle that.

Keep up your work.

Cheers,

Luc

author
burzurk (author)2017-06-07

BE AWARE. If you press hard, the platter will break/shatter into hundreds possibly thousands of pieces. This could easily take out an eyeball or two.

author
ThomasVDD (author)burzurk2017-06-10

Fair point. The 2 disks are stacked right on top of eachother for more rigidity, but wearing safety glasses is always a good idea while sanding.

author
burzurk (author)ThomasVDD2017-06-14

Thomas I'm not sure I know of an easy to identify which is which. Maybe just include the warning and why.

author
ThomasVDD (author)burzurk2017-06-15

I added it in the instructable, thanks for bringing it up!

author
schuimpge (author)burzurk2017-06-12

There's 2 types of platters commonly used in HDDs. Glass and Aluminum. The glass shatters and obviously you should test what your platter is made of.
But the aluminium is close to impossible the break. It's the coating on it that makes it so strong.
Having just destroyed my 2300 HDD's last week for a customer, not one single alu-platter broke during onsite breaking of the HDD's. the Cast Housing breaks, metal top cover bends and the platter bends.
Destroying the platters off-site after dismantling with a 15hp shredder only tears and rips the platters into mangled pieces. No breaking at all..
Been doing Electronics Recycling for 19 years now, check if it's not glass and you're ok

Cheers,
Luc

author
ThomasVDD (author)schuimpge2017-06-14

Thanks for the reply!
What would be the easiest way to check if it's glass or aluminium? I'll add it in the instructable as extra info.

author
schuimpge (author)ThomasVDD2017-06-14

Found a lot of ways to check it...lol..right here on instructables:

https://www.instructables.com/answers/Distinguish-...

Plenty ways to choose from.. Sound, light, neodymium magnets..etc..

author
ThomasVDD (author)schuimpge2017-06-15

Awesome! I'm adding it in :)

author
schuimpge (author)ThomasVDD2017-06-14

Hello Thomas, after you've taken out the platter / disk, (use gloves), just hold it slightly above an anvil or your workbench. Tap it with a hammer (light tap) and it will already shatter..

Need to check here if I can find some samples with a glass disk and see if there's any visual clues.. I think so, but need to confirm that.

author
jtechian (author)burzurk2017-06-08

Um, a hd platter is an aluminum disk. Cant see that shattering. You may be thinking of cd disk.

author
Nachtengel (author)jtechian2017-06-11

From what I've read.it seems the smaller 2.5" laptop hd platters are more often than not made of glass while the larger desktop pc HD have aluminium platters. Either way best to be sure - applying pressure to a high speed spinning disc is not the time to find out it's made of potentially lethal glass.

author
schuimpge (author)Nachtengel2017-06-12

Correct... Most 3.5" HDD's all still use aluminum, since it's less prone to breaking and easier to manufacture and has longer endurance, especially with high RPM drives (look for 15k HDD's that are used in server applications if you want really high speed sanding capabilities)

author
burzurk (author)jtechian2017-06-11

They have been made with different materials very very very old platters might bend..but those are well over 25yr old models AT BEST..they bend ever so slightly and will shatter.

author
schuimpge (author)burzurk2017-06-12

Current HDD's still use aluminium. The above mentioned HDD's where between 2 and 10 years old.
Once more: make sure you check if the platter is glass or Aluminium. If glass, get another HDD..

author
Nachtengel (author)jtechian2017-06-11

Most of the ones I've seen are made of glass and are very fragile and can break into very sharp fragments

author
jtechian (author)Nachtengel2017-06-11

I have salvaged Hard drives from the old 8 inch to the small 2.25 laptop drives and never found a disk made of glass. All I found were aluminum that is coated with a thin film of platinum and ferromagnetic compounds. I never even heard about a glass platter. Maybe they were made in the beginning of hard drive manufacturing. Never too old to learn huh!

author
Aviyahalom (author)jtechian2017-06-09

Actually, some hard disk platters are made of glass. https://en.wikipedia.org/wiki/Hard_disk_drive_platter

author
ajayt7 (author)2017-06-12

Interesting project, it makes us learn about many things. Thanks for posting

author
pjnovas made it! (author)2017-06-11

Awesome!, I tried it in using a radio with the ESC and it's pretty fun, I'm gonna think on other uses too. thanks!

20170611_191829.jpg
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Jankó PéterJ (author)2017-06-09

Helló. teljesen Tökéletes és Teljes jó megy Nagyon köszi szépen, igazán élvezze Már Örülök Neked: P

author
ym58 (author)2017-06-06

Actually, I've just tried with two different HD (one 'triangle' the other 'star'), none of them starts rotating.

My ESC and servo tester are standard and I use them quite often to bench test drone motors out of a 8.4V Lipo battery.

I even tried with a 12V bench P/S but to no avail ... no rotation.

Is there anything that I am missing ?

test_moteur.jpg
author
ThomasVDD (author)ym582017-06-07

Are you sure the motors are still fine? Wouldn't know the issue otherwise :/

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ym58 (author)ThomasVDD2017-06-07

Not quite sure and now it's too late to test them on a PC !

But I have a bunch of other HDs on the shelf that I'll test on a PC beforehand to ascertain the motor is OK before I hack them.

Will keep you posted.

author
zanod (author)ym582017-06-08

When you're running up the motor on a RC model, you always start from zero throttle then increase it. As you increase the throttle, the frequency sent to each winding increases, and the motor ramps up its speed. Maybe the motor just follows the frequency. Is there any feedback from the motor to the ESC to tell it the speed of the motor? There are only three wires. So if you tried to spin the motor initially with a frequency equivalent to running speed, it's quite possible the motor wouldn't turn.

author
ym58 (author)zanod2017-06-08

At power up, the tester's pot is at min position and the ESC bleeps the famous sequence "ti-ti-ti ~ taah-taah-taah-taah"

Then increasing slowly the pot makes the motor vibrate (and supply current increase to 350mA) for 3-4sec, then it stops vibrating and never rotates.

I've tried that both on a 8.4V/2S Lipo and a 12V bench P/S.

The HD motor I used for this test is a 3-pin 'triangle' type with a 3-Ohm coil resistance between each pin.

Instructables1.jpg
author
ThomasVDD (author)ym582017-06-09

Have you removed the circuitboard of the harddrive?
Maybe you could change the order of the wires. It didn't matter for my ESC, but you never know.

author
ym58 (author)ThomasVDD2017-06-09

Have you removed the circuitboard of the harddrive?

>

Yes


Maybe you could change the order of the wires. It didn't matter for my ESC, but you never know

>

Yes, have tried all combinations !

author
yesican (author)2017-06-08

To good to be true. Put three of these side by side and use them to sharpen blades. Check out "Stumpy Knubs" on the youtube. He has a mod of an existing sharpening station build in the same configuration as this sander but bigger. We're going to build tonight. Thanks and keep making

author
ThomasVDD (author)yesican2017-06-09

Good luck with the build! Post a picture if it's finished :)

author
CaitD1 (author)2017-06-06

I love this project. I've been needing a small horizontal grinder for polishing some lapidary projects. Got lots of old drives around here, so this is exactly what I needed. Many thanks!

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ThomasVDD (author)CaitD12017-06-07

You could make several, each with a different grid of sandpaper :)

author
CaitD1 (author)ThomasVDD2017-06-07

Even better, I could use that velcro like stuff they put on sanders today and then just switch the papers. Actually for the stones, I need diamond discs, but the ones I have are the velcro backed kind. I just saw the replacement hook papers in the hardware store. This is my very next project. You really got my creative ideas flowing with this one. Thanks.

author
zanod (author)CaitD12017-06-08

When Velcro parts are mated, there is a sponginess in the Velcro itself, which means that if you run a stone against it, you will wind up with a convex surface instead of a flat one.

author
CaitD1 (author)zanod2017-06-08

Interesting, I had not thought of that. I just checked those special pads and I can see exactly what you were referring to. Thanks for the heads up.

author
zanod (author)2017-06-08

Anybody got an old IBM 3330?

author
RichardR2 (author)2017-06-06

Thanks, now I finally have something to do with all those old hard drives I have sitting around.

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ThomasVDD (author)RichardR22017-06-07

Glad you liked it :)

author
ndpani (author)2017-06-06

Very useful tool in any workshop. Thanks for the details.

Dhandapani

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ThomasVDD (author)ndpani2017-06-07

Glad you liked it!

author
TSJWang (author)2017-06-06

ur a genius

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ThomasVDD (author)TSJWang2017-06-07

Thanks :p

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autotech1 (author)2017-06-06

I spent hours removing hard drives from computers that my wife's ex employer wanted the discs destroyed for security purposes, taking them apart and salvaging what I wanted. As I disassembled them I tried to figure out how to get the motors to turn but I had no luck. I couldn't find anything on YouTube to help either. I wish that I had had this instructable then, because I ended up recycling all of the cases after I removed the spindles and magnets from them.

author
ThomasVDD (author)autotech12017-06-07

Well, 10 sanders wouldn't have been that useful either :p You could always make a custom enclosure for the spindel though!

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autotech1 (author)autotech12017-06-06

I kept the power supply from each of the computers too.

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msameer39 (author)2017-06-06

Good. Voted for your project. Good luck

author
ThomasVDD (author)msameer392017-06-07

Thanks!

author
bmiller91 (author)2017-06-06

Realistically how long will the motor hold up to this type of use?

About This Instructable

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Bio: I study (civil) electronics engineering at the VUB in Belgium. I have a passion for making things, both useful and cool.
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