Drill bit question ...

[Arfa Daily]

Dead easy one, I hope, for thems in the know ...

I need to drill about 4 or 5 holes of around 3 to 4 mm in some stainless. It's not very thick - 0.5 mm perhaps ? Certainly not more than 0.75, anyway. It is good quality stuff though, and *very* hard. It's actually a stainless steel professional kitchen prep table. The last time I tried to drill anything similar, I wrecked a number of drills in short order.

The holes I need to drill are in a vertical surface, which doesn't leave any easy options for any kind of lubrication or cooling. So, the question is, is there a type of drill bit that will go in a standard (decent) DIY quality electric drill, and will survive long enough to drill this small quantity of holes in this material, and doesn't cost an arm and a leg ?

Pointers to specific items from anyone with experience in working with this difficult material, greatly appreciated.

TIA ! :-)

Arfa

[The Other Mike]

Centre punch, lubricate, high speed on the drill, lots of pressure, no pissing about taking it easy as the material will work harden quickly.

[Bob H]

Also use some kind of cutting paste, and apply it little and often to help the drill, and stop burn out.

[The Medway Handyman]

Wot he said :-)

[Dave Plowman (News)]

Start with a sharp drill, a low speed and lots of pressure. I take it it's not practical to use a drill press?

[dom]

Recently been fitting tubular (A2) stainless steel bannisters, 2.5mm tube w all thickness. Needed 6mm holes for mounting brackets. Started at 3mm using Bosch TiN bits. Initial hole hardest, opening out easy. Used a decent high torque cordless drill and quite a bit of hand pressure.

[dennis]

Is it really that difficult? I put eight 4 mm holes in some SS sheet using a drill from the lidl set and a battery drill and I didn't see any problem. It only took a few seconds for each hole. It was SS sheet too as its outside in the garden and still nice and shiny after two years.

[Andrew Mawson]

Some grades of stainless steel 'work harden' at the drop of a hat. The secret is to drill slowly, use oil, and don't let it overheat. If by chance you end up with a work hardened spot 'just where you want to drill' sharpen a masonry drill and use that.

AWEM

[The Other Mike]

A 3 - 4 mm hole with a standard cordless or corded drill on its *fastest* speed (circa 1300 - 2000rpm) will come nowhere near the optimum cutting speed for any readily available stainless. All low speed (circa 500rpm) will do is lead to pussyfooting around and ultimately work hardening.

I was drilling a 22mm diameter hole in a 10mm piece of 316 only a couple of weeks ago. The drill bit was probably 20 years old, Used maybe 250rpm on the pillar drill. Lots of lube. I make that around 56 feet per minute, less than half that usually recommended. I followed it up with a number of 6mm holes in the same material at around 1500rpm.

A 4mm hole (as the OP wanted) at 56 feet per minute equates to a drill speed of around 1300rpm

[Dave Plowman (News)]

I don't get that. A drill has to cut its way through the material, so using a very slow speed may make the whole process slower than optimum - but won't do any harm. My pillar drill is left permanently on its slowest speed. The important bit is to use enough pressure so the bit cuts rather than just skidding across the surface. Which can be difficult hand held.

[The Other Mike]

Yes at a lower speed it will still cut but with the slower cutting there is a tendency for users tend to back off the pressure and take it far too steady and they actually intitiate the work hardening rather than avoiding it altogether.

[Dave Plowman (News)]

Right. I'd say it *far* more likely with a high speed.