Recycled HDD Powertool (Disk of Prometheus)

UPDATE 09/04/2011: Hey guys, I have entered the Disk of Prometheus in the Green Living and Tech. Contest, Please VOTE for me!!

In my last instructable related to recycling old HDDs, I had designed a sander from a junked HDD for as little as $5. But, the old design had its limitations and i had got a lot of people writing to me about improving the design to increase its usefulness. You can find the old instructable here

The older HDD sander had its motor still attached to the HDD base, thus limiting its use. In this instructable, we're going to design a power tool using an old hard disk , which can not only do sanding, but also cutting, polishing(buffing) and it may also be equipped with a diamond blade to cut glass.
 
The HDD motors spin at a very high RPM, but do not have much torque,but once they get into full speed('bout 7200 RPM) it is enough for our grinding/ sanding/buffing etc. purposes.

WARNING: The HDD is not a plaything. The platters spin at a very high speed, making it easy for the sander to rub your finger raw. I am not responsible for any damage you do to yourself or to anyone else near you.

Step 1: Materials Needed

For the project we are going to need some cheap stuff. The list is pretty much same as the old HDD sander with a few additions.

Parts:

• A junked HDD(needs to spin up!!)
• ATX PSU
• A Wooden ruler
• Wires (single-core preferred)
• Zip Ties (VERY IMPORTANT)

A wooden ruler may be difficult to come across nowadays. So, a piece of wood with the same dimensions will also suffice.

Optional: (for more info. go to Step 7)

• Sponge
• Diamond-edged Blade
• Sand Paper

• A brushless ESC like the one here (Step 8, Part 2)

Tools:

• Torx Screwdriver set
• Power Drill
• Soldering Iron
• Soldering hot plate(optional)

Comments

[lenny25]

Have you actually sanded anything with it?

Cool idea, but me thinks there is no way that little motor will have the torque to sand anything. 7000RPM is super overkill for sanding, so what this needs is some gearing. That will also increase it's torque a bit.

RPM is nothing without torque: there is another instructable about a tesla turbine that spins at something ridiculous like 60 000 rpm, but the guy holds the shaft between his index finger and thumb and brings the turbine to a halt.

[pfred2]

My angle grinders are 10,000 RPM so you were saying? Yes they have sandpaper and even flap discs too.

[lenny25]

What i'm saying is that your machine can run at 3000RPM, 7000RM 10000RM it makes zero difference in the ability of that machine to cut or grind anything. That depends on the power/torque of the machine. As I said telsa turbines can 60 000 RPM and you can bring that engine to a stop between your index finger and thumb. The reason is it has almost no torque. I'm just saying talk about RPM's is irrelevant. What can this motor do in terms of actual power/torque? If it's previous job was just to spin a aluminum disk at high speeds with not real resistance or work needing to be done, then I doubt it will be any use for this application, unless you invest some serious attention to gearing!

[pfred2]

Surface speed is a vital component of sanding and grinding. There is a direct relationship between RPM and surface speed as can be seen here:

SFPM = (PI X DIA X RPM) / 12

When rating motors the RPM is a determining factor how power is stated too. One formula is:

HP = (RPM X Torque) / 5252

So I'm not sure where you came up with "power/torque"?

[jarvallmighty]

Great idea... but has flaws. My first problem is the lack of a guard or shield. All grinders, polishers, cut off tools, ect. have a scatter shield. Small rotary tools dont but I hope everyone has safety glasses when needed. Like ALWAYS. Also mounting system seems iffy at best. I would try 2 rulers, flat sides together with a bead of rubber or silicone on the flat sides and clamped light but enough to sqeeze out excess. Should give some harmonic dampening. Never use the glass disks ever, never ever! Easy way to tell is tapping the disk with a small metal rod and if its glass it will make a high pitch Tinck noise. Any others will make make more of a Thunck noise. Still not sure then dont procced. If you can get this refined and if any of my help helped you than great luck to you,Jarv

[dudenitx]

hey, dude,,,

u just gave me an idea to have my own buffer.


thank u..
keep up the good work
GOD BLESS U,,,

[DIY-Guy]

As cool as this is, I wonder about safety with such a thin piece of wood as a mount. How can this be improved to protect the user from a shattering drive disk if and when the handle breaks? Commercian sanders have covers on at least the back side to help protect from flying shards if an accident occurs.

Any ideas anyone?

[zia0007]

There are two types of disk platters - glass based and aluminium based - if I am correct. Using the alluminium one would not shatter. If I am correct??

[mhkabir]

Yup!

[arpruss]

Do you know a good way to tell whether your platter is glass or aluminum?

[dasraiser]

get a magnet and run it across the surface, if it's aluminium it will resist you motion.

[mhkabir]

Nope, aluminium in non-ferrous, so it is not attracted by a magnet, due to the molecular structures that it forms. No magnetism, no resistance

[arpruss]

Won't a glass one do that, too, if it's coated with something metallic, which it probably is? Or is the thickness of the coating not enough to resist the magnet's motion?

[dasraiser]

the coating would to some degree attract the magnet, but by wiping a magnet across the surface the interaction between the magnet and platter; if aluminium should produce a breaking force and glass should not, although im not sure if the coating will act as some sort of shielding, if you have a chunk of aluminium (most hdd are cased in aluminium) you can feel this magnetic interaction for yourself and hopefully feel the same on the platter.

well i just tried it myself, one platter was out of the disk (was going to use it for fs mirror) and had no feel of force, the other one that was still attached did, but was quite weak, both had no surface attraction either, so in conclusion, it would be quite a tough call, i think ones glass and the other aluminium, but not 100% sure by any means.

[noingwhat]

Forgive me if I missed it, but what was the point of keeping the PCB? Wouldn't it have been easier to use a multimeter to determine how much power is needed for the motor, and feed it that instead?

[mhkabir]

Well to dumb it down, the HDD uses a brushless motor, which needs a special controller to drive it, which is the "PCB"

[noingwhat]

Thanks for the information by the way, I can't believe I didn't say this earlier, my bad. Great instructable, I always love making new things out old/broken/spare parts, and it just so happens I have a broken hdd laying around somewhere, if only I could find it...

[noingwhat]

I *just* read up on this, so correct me if I'm wrong, but from what I understand, the brushless motors need the pcb in order to switch between positive and negative, a process typically handled by the brushes, so theoretically, wouldnt it be possible to build a simple citcuit, maybe something similar to a 555 timer which would be able to carry out the same task? I understand for the sake of simplicity using the board that comes from the hdd, but i am just kind of curious about what can be done to shrink down that gigantic big board on the back of the handle, or in order to easily replace it if it were to ever break, of course, this is all of course assuming you are basic-proficient in circuitry.

[vadipp]

"You could get a brushless ESC, those used in R/C boats, aeroplanes etc. and attach it to your motor, and remove the original controller completely." as mentioned in the post.

[sunshiine]

Nice presentation! Just peeking in on you! Wanted to see your flare! Nice job!

[mhkabir]

Thanks! Please Rate and Vote!

[sunshiine]

done!