I needed to make some 3.2mm wide slots x 8mm deep into two steam valves. I have a 1/8" slot drill but the flutes are only 6mm deep and also it was important that the slot was no wider than 3.2mm. So I sacrificed a 3.0mm drill cutting it roughly in half and super gluing it into a 8mm dia. brass rod 30mm long. I ground the drill end flat. I was cutting into brass and made 0.010" cuts on each pass. When I was at the full depth I indexed 0.003" on the 'Y' axis until I had the 3.2mm slot. Job done.
