On 11/08/2019 14:49, brian wrote:
I need to drill 30 oddÂ* 4.5mm holes in a stainless steel pipe; I'm
drilling a small pilot hole ~ 1mm first . Usual type blunt too quickly 4
holes !Â* Pipe wall thickness isÂ* only 1mm and I thought I'd get away
with it.

Carbide tipped and cobalt seem to be recommended . Will tile drills do ?

Any experience or advice ?

Stainless steel will work harden so you need to keep the pressure on the
drill as you feed it in.

The idea is to be cutting the next bit before the previous bit has had
a chance to work harden.

DO NOT PAUSE in the drilling, keep going !!!!!