Many years ago, I acquired a pile of tiny, drill-bit-like items that I use to make practically invisible holes in drywall to hang lightweight stuff from. They are indispensible, but I don't know what they're called. I got them from my dad, who in turn had received them from our dentist. They might be used in dentistry, or they might be from said-dentist's hobbies. I'd love to know the origin of this item!
Looks like endodontic files, or root canal tools if you prefer laymans terms.
You can probably find such tools on eBay if you want.
Not to be repetitive those are files or broaches , not drill bits. They cut on the flanks by rotation and axial movement . A drill bit (should) only cut on the end. A drill bit does not have an enlarged shank for holding. I have several bits in that size range ; they require a collet to hold them. I never found a use for them except the larger ones are good to clean carburetor passages.