Step 1: Supplies
-Small grinding attachment
-Wire wheel attachment
-Sand paper (or sponge)
Not puictured: Image editor (ie: Photoshop, pencil)
SAFETY NOTE: We're going to be using a Dremel tool at higher speeds, and small bits of vinyl will fly everywhere. I thought my normal glasses would be fine for this task, but the high speed debris hitting my eye proved me wrong. Play it safe and use something with full coverage.
Step 2: Create the Stencil
Measure the diameter of your record. Not all 12 inch LPs are created equal. Mine happened to be 29.65 cm
Find a picture and copy it into Photoshop (or some other image editor). Get rid of everything you don't want, and resize it to fit your specific record. Print it out, cut it out, and tape everything together.
My stencil is covered in packing tape on both sides. I'll probably reuse it, so having something laminated (so to speak) will be reusable.
Attach it to the record (I used more packing tape) to keep it in place.
Step 3: Trace the Stencil Onto the Record
You can easily smudge the graffite, so take care when your handling the record. Once you're done, any left over marks can be wiped wiped off. I'd bet a silver sharpie would work well, but it'd be more difficult to clean up afterwords.
Step 4: Start to Cut
Fire up your dremel with the grinding bit attached. You can only subtract here, so take care not to cut out more than you intend to. We'll do some cleaning up with the wire brush later, so don't worry about making everything perfect. At least not yet.
One thing you will quickly notice is melted vinyl forming burrs on one side of the cut as you move the tool. If you can, orient the tool such that the burrs collect on the scrap side of the cut.
Step 5: Grinding and Sanding
After you're satisfied with the wire wheel, go around the edge with some sandpaper. I used a 180 grit sponge. It was what I had on hand, but it also kept the surface from getting too scratched up.
Step 6: Mount and Enjoy
Now step back and appreciate your work. Lather, Rinse, Repeat as desired.
Step 7: Inspiration!
I've seen small adapters made from vinyl used in jewelry before, and that's where I got the idea. Here are some more pictures to give you some ideas. And if you haven't seen the other instructables that teach you how to make clocks , bookends , or bowls from records, take a look. Think of what you could make if you combine the methods!