This is an idea that I came up with while taking apart old hard drives for fun. It turned into a regular thing and now I've got the process down to a science. Here's how I do it. I also sell them at http://www.etsy.com/shop/Yooderstuff
For this Instructable, I'll be using an old WD Caviar hard drive. Drive designs differ, and some are better for this project than others.
You will need:
Torx-6 and Torx-8 screwdrivers
Phillips head screwdriver
Drill and bits
3/4" clock movement
Next, undo the screws around the edges that hold the cover down, but don't go tugging yet. There is at least one more screw hiding under the stickers. One in the center, and one off to the side. Refer to the pictures to get an idea of where it'll be. Feel around and then cut through the stickers to get to the screws.
Once you've gotten all the screws, you can cut through the tape around the edge and open it up.
Step 2: Disassembly
Now it's time to free up the actuator. To do this, remove the two screws securing the top magnet, and remove it with a pair of needlenose pliers. Don't try it with your fingers. It won't work. Place the magnet far away from anything electronic.
Then, remove the single screw keeping the actuator retainer in place. Work the retainer up and out. The arm should swing freely now.
Now, undo the screws holding the platters down. You may have to hold the edges of the platters to keep them from spinning. Once the screws are off, turn the drive upside down on a soft cloth and the retainer, platters, and spacers will fall out neatly. Leave them alone, in that order.
Next, unscrew the motor assembly and pop it out.
Step 4: Pre-modification
Now it's time to make sure everything is in order to make your modifications. Line the drive body up on top of the cover, and mark where the mounting holes are.
It's also a good time to spray paint your hands, if you don't want them the stock color. I went with black.
Step 5: Modification
Time to break out the hammer.
Place your motor assembly upside-down in a vice (preferably padded) with the spinning part hanging freely. Place an old screwdriver or something of the sort in the center and tap it with the hammer. Eventually, the whole spin assembly will fall out. Sometimes this step takes two taps, sometimes it takes ten minutes. Be patient.
Once you've picked up your motor, place it back on the vice, this time right side up. Repeat the previous step, and the spindle will pop out, along with some bearings. Make sure to get all the bearings out. If the top piece (edged by some blue adhesive) stays in, don't worry about it.
Step 6: Modification
Now, take a 5/16" drill bit and ream the motor base.
Reattach the motor base to the body, and use the hole as a guide to drill straight through the circuit board on the back.
Switch bits for a moment and use as 13/64" bit to drill two holes on your marks in the cover.
Step 7: Reassembly
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Now the clock begins to come together. Screw the motor base back into the body of the hard drive, if you haven't already.
Reassemble the platters and spacers on the mount, and screw them back in.
Place your reassembled platter assembly back where it belongs, and move the actuator heads back into place.
Affix a 3/4" clock movement (I use Walnut Hollow) through the hole in the drive, and tighten the nut.
Step 8: Reassemble & Finish
You're almost done. Flip the drive over, and use two hard drive mounting screws to secure the cover (now the base) to the bottom.
Make sure your movement is set to 12:00 and attach the hands as directed.
Put in a battery, take some glamour shots, and you're done!