This is my take on Mrballeng's crescent pendant (which I'm sure y'all have seen already). It's a bit less shiny, but hey, what're ya gonna do.
The other day I saw his 'ible again and realized that I could make something similar to it using an old woodturner's trick. Actually, I think the reason I tried it was because of his comment that the methods he used were somewhat dangerous and he didn't want people getting hurt. So, naturally, I saw it as a challenge to make one without killing myself.
WARNING and all that: Use appropriate caution and attention to safety when working with power tools. Always know what your tools (and you) are capable of and don't make things do what they're not designed to. If you're unsure of your materials' structural integrity, please, at the minimum, wear a face shield. And it goes without saying (and yet here I am, saying it), ALWAYS wear safety glasses.
Step 1: Prepping the Wood
Here I'm using some osage orange that my dad and I slabbed into ~1" thick pieces with a chainsaw. A 2" x 2" or so square was cut from one of the slabs and trued up on the lathe.
You'll also need a glue block, I'm using a piece of 1" x 2" pine here because it's what I had, but you should use something that doesn't splinter very easily (maybe poplar or whatever else you have on hand). I had problems with the osage coming off because the pine splintered where the glue line was.
Cut a section of the glue block material a few inches long and mark the center. Use hot glue, CA, or something else you trust to glue the puck of osage to the block, trying to keep it as centered as possible.
Now remove two jaws opposite each other from your chuck, and mount the block assembly.
Step 2: Turning the Outer Circle
This is where you get creative, so do whatever you want.
I turned a shallow dome, sanded through 400 grit, used EEE (a wax that contains particles of tripoli compound, a micro abrasive) for a nice shine (get it? EEE - triple E? ...ahem. sorry), and finished with Renaissance Wax.
Step 3: Turning the Inner Circle
Now shift the block a little bit to one side and see if you like the new center. Keep shifting it around until you're happy where it is. It'll be a little out of round, so just stay within your comfort zone in terms of speed. But don't make it too slow, because speed is (usually) your friend. My biggest problem when starting out was that I always kept the speed too low and never got a nice finish on my pieces because of it.
Step 4: Drilling a Hole
There are a few ways you could drill your hole. I chose to just move the block a little further out of round and use a drill bit held in the tailstock, but you could also use a drill press or hand drill to achieve the same goal.
No matter which way you do it, since you're most likely gonna be drilling through rounded surfaces (i.e. not perpendicular to the drill bit and thus likely to wander), I'd recommend inserting the bit almost all the way into the chuck, leaving maybe 1/4" sticking out, and tightening the chuck loosely so as not to damage the flutes. Carefully drill a shallow hole just to start it, then place the bit where it would normally go and drill the rest of the hole.
Step 5: Parting Off
Start to shape the back, working from the outside in. Once you get too thin in the middle, you can't really go back to the edge to fix anything because you will end up with a lot of chatter marks. When you've got down pretty far (maybe a 1/2" to 1/4" diameter attachment point left depending on what glue you're using), sand and finish the rest of the back, then use a thin parting tool to completely part it off. Sand as necessary to achieve the finish you want (I just sanded with 150 grit and called it a day, as there were no noticeable scratch marks and I rather liked the matte finish).
Step 6: Other Options
If you don't have a lathe, you could probably do this with a drill press by drilling 1/2" or so holes in the block (whatever fits in your chuck), gluing in dowels or metal rods (I would recommend rods if you're planning on making more than one or two of these), and chucking up the rods for each offset. You might need to vary the lengths of the rods though, so you can leave all of them in place without hitting the chuck.
As usual, be careful. Keep in mind that the bearings in drill presses are not meant to sustain sideways pressure, so I don't really advise you do this too much. I don't know whether or not this will work as I've never tried it before, so use at your own risk. If in doubt, just find a local woodturning club and I'm sure they'd be happy to let you use one of their lathes.