How to process the 0.3 hole?

It is recommended to use circular drilling for machining. I once processed a 0.3-hole optical fiber probe with a depth of more than 4.0mm, made of SUS303, which set a drilling record of single drill 160 PCs. The key lies in feed (F0.065,438+0), cutting depth (0.65,438+0) and rotational speed (high speed >: 2500), and it is also important to control the flow (impulse) of coolant. If the drill bit is too small and the flow rate is too large, it is easy to break.