On 11/08/2019 15:08, nightjar wrote:
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 ?

I wouldn't try them.

Nor me


Any experience or advice ?

Brian

I does slightly depend upon the grade of stainless steel. However, what
is usually important is that the drill is not allowed to dwell during
the feed. That quickly causes local hardening of the steel, which blunts
your drill.

Agreed

Ideally, use a powered feed, having first looked up the speed and feed
speed in one of the many available charts. If you have that option, use
solid carbide drills and flood the work with lubricant.

Both overkill?

Failing that, use a pillar drill, use a good lubricant and keep a steady
pressure on from start until break through. Trying to drill most
stainless steels with a hand held drill is simply asking for problems.

Agreed, pillar drill is a far better bet. I've always been impressed
with the new cobalt drills. For 4.5 mm, fairly low speed and firm
pressure. 3-in-1 should work, or Toolstation do an aerosol cutting and
tapping fluid.

eBay item 183034379363 is £2-75 for 4.5mm. I'd buy two or three to be on
the safe side (although I reckon you should get 30 holes out of one).