I am looking to do some very small milling, an aluminum coin face.
Can someone point me to the small cutting tool size / cutter that theroreticalyl could work?
I already own the .0625 cutter which is very small, does smaller exist?
Carbide 3D stocks the #122 .0312" Flat Cutter at https://shop.carbide3d.com/collections/cutters/products/122-0312-flat-cutter-qty-3
For micro-machining, the Precise Bits folks are the best resource I'm aware of: http://www.precisebits.com/ --- let them know what you want to do and they'll gladly help.
The smallest I have used is 0.015" (0.4mm was what I wanted... the imperial was a lot cheaper and within 20 microns nominal) ball end from McMaster. Cost about $30. I did a fine job on aluminum, but I tore it up on FR4 copperclad board (dulled out due to improper feed). Square end are a tad less expensive.
smallest i use currently is 11 mil square end mill. i have also used 5 mil end mills this is only for etching PCB material.
T-Tech also has tools this small and good quality:http://t-techtools.com/store/index.php?main_page=product_info&cPath=8&products_id=156
you can also find them at McMaster-Carr but not as small: