A little help?

On the heels of selling not one but two bracelets in the last couple of days (thanks, you know who you are), I was going through my shiny bits of this and that and remembered that I have a bunch of old cuff links like in the photo (which are not mine, and come from this Ebay listing).

Can anyone offer advice as to what's the best way to make these flat on the back side? There are a couple of kinds here, and I've got a few of the snap cuff links as well. As an aside, those snap cuff links continue to be a very hot item on Ebay. They often sell in lots and will go for $2-$3 per face (with four faces per pair of cuff links - some are singles or half of a pair). Anyway, if you've got a drawer full, they'd sell on Ebay in a hurry.

While I'm at it, every time I look on Ebay for this kind of thing, old watches as well, I wonder about the supply. For my purposes, is it practically infinite? It seems that way. One could figure that every adult in the US, during the time people used mechanical watches, had at least one. Even when they stopped working, people (it seems to me) usually put them in a drawer instead of just throwing them away. As for cuff links, men and women would have several pairs.

Anyway, if we call the bottom row Row 1, I've got both kinds shown in Row 2. The kind with the stem, and the kind with the little hinge. Many of the ones with the hinges especially are the right size for use in the bracelets, and I've been sitting on them waiting for them to alter themselves with no luck. I do have a chordless drill that I could attach a cutting wheel to, but I would need to buy a vise, which I could do. Holding the piece with a pair of pliers quickly became NOT the way to do it. No finger slicing, please.

So if you've got two cents to throw in, please do. I'd like to incorporate these shiny bits into the bracelets.