milling fine detail in metal

Hello,
This is my first letter to this group
Over the past few years I have built a small desktop X-Y-Z milling
machine. I am currently using it to prototype jewlery in WAX.
I am reasonably well on top of the software electronics and mechanics
of the system.
I have it working to a accuracy of about 0.1mm. To mill wax 0.5mm
(0.02inch) broken drill bit works quite well. At this stage however I
would like to mill brass (or another suitable metal) Ideally I would
like a milling depth of 0.5mm but I can set the machine up to do it
in multiple passes.
Does anyone know if there are bits available of this size to mill
metal (perferrably without using liquid cooling or forced air)
I would appreciate any advice on this topic.
Thanks.