Step 1: Collect Your Tools and Materials
Step 2: Clean the Cards, Then Make Smaller Pieces
Now that they're clean, cut each gift card into 6 relatively equal pieces. Make one cut the long way, then cut each half into three pieces. You should end up with 6 vaguely squarish pieces. If you want to get precise about it, you can measure and mark and then make your cuts, but I find it's less time consuming to just eyeball it when I'm making a bunch. If you're making it for a big finger, you should measure and mark, to make sure you have enough material to fit the finger.
Step 3: Make Little Holes, Then Make Them Bigger
At this point, you might be asking yourself, wouldn't it be easier to glue all the pieces together first, then just drill one hole? Excellent question! The answer, in short, is no. At least that's the case if you're using cyanoacrylate. I've found that the torque of the drill always shears the last 1 or two layers off the block once they're glued together, and there's not really a good way to clamp it all together, since you're removing most of the material from the center. I've tried starting with smaller holes and gradually working my up. Doesn't work for me with the tools and materials I have. So I cut them one at a time. Doesn't take that long, and saves a big headache and much cursing.
Step 4: Time to Glue Your Fingers Together!
I prefer the gel type of cyanoacrylate. It's much easier to control, and I can use the nozzle to smear it around to make sure it covers the whole face.
Basically, I glue half of them together colored sides down, the other half the same. Then flip one half over and glue the backsides together so that the colored parts of the cards face the outside of the ring, with the dividing line right down the middle. I find it gives the final product a more uniform and defined grain.
Step 5: Caution! Warning! Alert!
Step 6: Evening It Out
The first part you want to carve is the center hole. Using whatever tools you have, even it out. If you don't have a rotary tool, use the knife to even out and enlarge the hole to whatever the final size should be. Since the holes likely aren't the exact same size, and you likely haven't glued them together perfectly aligned, make them even now. If you don't have a rotary tool, use the knife to cut away the excess and carefully enlarge the hole until it reaches the desired size and shape (preferably round). If you have a rotary tool, use the carving bit to enlarge the hole just enough to fit the sanding drum inside.
Then use the carving bit to even the outer edge of the ring. You're not doing any real shaping just yet, you just want to even out the edges to see how much material you have to work with.
If you have a rotary tool, use the sanding drum to enlarge the hole. It should be fairly easy to keep the hole round. Check the size frequently. Luckily, my pinky is the same size as my girlfriend's ring finger, so that part's easy for me.
Make sure you get the size right now. Or if you need to resize it later, use sandpaper only. Once you've finished the ring, the band will be fairly thin, and trying to resize it with a rotary tool will heat the plastic enough that the ring will deform. Then you've got to start all over.
Step 7: Shaping the Ring
Once you've determined which corner that is, sand/rasp/file down the others.
For these, I think a nice flat top with some gentle curves looks good, so that's what I'm making in the following pictures. I generally taper the band down about 3 layers so the band is narrower than the head, but not too narrow. If you're using a rotary tool, and it has variable speeds, turn it down to it's slowest setting if you're worried about taking off too much material, then gradually turn it up until you're comfortable with what's happening.
You'll also be refining the design with the files in the next step, so feel free to leave extra material, and don't worry too much about making mistakes. Mistakes give the ring character. Or something.
Step 8: Final Shaping
Use the files to refine the curves and take off the rest of whatever image or logo was on the front of the gift card. File down any raised areas and use it to shape the "grain" of the ring.
Step 9: Final Stage! Sanding!
Step 10: Check Your Work
If you're happy with how it turned out, you're done!
If not, don't blame me, you made the thing.
Seriously though, if you or whoever you gave it to feels it coming apart anywhere, don't wait. Squeeze some glue between the layers and reattach them. Then go over them with sandpaper again until smooth.