Making thumbrings without pain...

From the photo you embedded it looks like you made a beautiful thumb ring but you designed it to function incorrectly. If you are positioning the string between the black ridge and the lighter tab on the ring you will be putting all the draw pressure on the last thumb bone. So the pressure is mostly applied to your thumb print area. That would be extremely painful even with a moderately heavy draw weight. The thumb ring is designed with an oval opening so that it can be slipped over the oval shaped end of the first thumb bone (the one attached to your hand). But when twisted 90 degrees into its functional position it cannot be pulled off without crushing the flange of the bone. That would take well over a hundred pounds of pull even for dainty bones. Nearly all the pressure from drawing the bowstring should be on the 2 red areas which are shown in the photoshopped x-ray I attached. If you pinch those two areas with your other hand and pull as hard as you can you will feel no discomfort. That's more or less the way a correctly fitted thumb ring should feel. This works best when the string is pulled by the upper lip of the ring and slightly above the joint. I pull a 70lb at 28" Hwarang well past 85lbs with no thumb discomfort. Bending your thumb and holding it with your index finger is really only to lock to draw. If your thumb ring can come off at all in its shooting position none of this works. Hope this helps.

Hey guys, just a follow up on the problem in case anyone else searches about this.  The leather on the back was extremely successful, but since I'm making the rings I wanted to understand the physical attributes for comfort.  I came up with this ring (after a few more trials and errors).  Essentially, the comfort increased from the wider band around the thumb, a "contour" on the back of the band (for release comfort; bottom picture on the bottom of the band), and most significantly, I made the inside diameter slightly smaller and also rounded the inside shank (like a wedding band).  This forces it to seat slightly lower on the digit.  I have fat thumbs, but in draw the string part of the ring is exactly the same length as my thumb, so the string can't touch my skin  (the pictures make it look short...camera adds 20 lbs).  I shot about ~150 arrows from it with absolute no pain except some minor rubbing (I have soft mooshy IT nerd hands :\)  Critique it if you guys see something I could improve on.

Also this would be nothing without pictures, so here it is!

Under the thumb pad is a tendon that curls your thumb, an ill fitting thumb ring can put too much pressure on this tendon and can cause soreness. That's why some thumb rings have a cut-out here, to make space for this tendon.

Bleeding at the back of the thumb can be because the ring cuts off blood circulation because it's too tight when curled up for use. The ring should have a bit of space at the back (maybe only visible when you press the ring against the string) that lets your thumb  breathe.

The ring should rely on ellipsoid lock on the joint rather than overall tight fit on your thumb.

I think the string is supposed to rest on the thumb ring, not actually touch your thumb, but I wouldn't know for sure. I use a tug-ggakji (턱깍지/chinned thumb ring) http://www.smgung.co.kr/2010/image/r_2010_23_1.jpg

Just has a full ridge that stops the string riding up and also makes room for that tendon