Yes, as Mechman says you've got into the work hardening problem, where the tip of the drill skates on the surface of the hole and no amount of rotation will progress the drill forward. Pressure is your friend, by which I mean drilling a smaller hole. But then the drill is (disproportionately) more fragile. If it cuts through the hardened area (which is a big if) it's likely to snatch and break, and that's if you can avoid putting side forces on the drill, which will also break it.

Having drilled a pilot hole it's not guaranteed you can drill it out to size, that material is going to grab the drill and snatch again, always supposing you can get under the hard skin.

Cutting oil or coolant would have helped, but are now irrelevant. You needed pressure on the cutting edge to keep it cutting. Once it skates you're lost.

I wonder if you would be better off going abrasive. Having got the hole area work hardened I'd rather have a go with a carbide bur in a Dremel kind of tool. Keep the area wet to keep the tool from burning out, but you should be able to make progress, if slowly. Once you've got a hole open it out – if need be with a stone point (they sell grinding burs for sharpening chainsaws – they have all sorts of other uses).

Carbide drills or carbide tipped drills both need lots of pressure, so you're fighting the inevitable trying to use them in a hand drill. And, as you say they are very brittle so sideways pressure will shatter them.

Good luck

Simon

If you are using a hand drill you could try using a 'tipped ' masonry drill, sharpened up as many times as necessary until you are through.

Hand sharpened masonery carbide drills will do it but if the stainless is like the stainless on the jaws of your cheap hand held verniers then you need a heck of a lot of pressure to get through

I needed to use my drummond M on the backgear to drill those stainless jaws which are about 3mm thick

We had to drill stainless steel for a pop rivet to lock parts of a springbox used in the tail of the Hawk trainer jet. The best method was slow speed and high pressure with a sharp drill. It was done dry, as oil would contaminate the assembly and make the drill swarf difficult to remove.

For austenitic steels a sharp drill is vital. A cheapie is going to lose its edge quickly and that's where the rubbing and the trouble starts.

My elderly Dormer booklet recomends stub length drills with a point angle of 135-140 deg.

Slow speed and heavy feed-rate.

I've seen that method suggested for drilling glass.

I have had similar problem when drilling stainless, it work hardens and the drill just skids, I tried cobalt drills without any success, I did have success with diamond core drills, slow but eventually successful. Arc Eurotrade sell a limited range of sizes, depends what size you can manage with, maybe adjust size of your fitting to suitable core drill size.

Dave W

Electric drill is going to be way too fast for this job.

If things could be held stable enough (big if) an old style "belly braced" hand drill would probably do the trick. Lean on it hard and turn steadily in high gear. I keep a nice one, with enclosed gears too, on the shelf for such emergencies when its the only way. Perhaps twice a decade! Apart from holding things steady the main issue will be chuck grip on the small drill. The old style hand tightened chucks were never known for being really tight holding.

Same principle as the Cole "clamp on the job" ratchet drill **LINK** trick of drilling through a bearing race with a sharp masonry drill. The Cole has screw feed and can generate up to 500 lb or so pressure on the drill. Somethings going to move.

Ideally need a different drill point grind shape for slow speed high pressure drilling. Razor sharp but more clearance to ensure the edge lasts. The conventional point puts a bit more emphasis on plenty of metal close to the edge to take heat away at high speed. The aboslute razor edge coming straight off a good sharpener is normally soon lost. Still very sharp but ….

Clive

Its Hard work but not this hard.

Need an old fashioned corded drill with two speed gear box. trigger control helps more.

use good drills Dormer A002 work well, they are like a split point multi facet, use cutting fluid like Rocol or CT90.

I was doing M10 Tapping size in 316L 10mm thick. 4 holes per plate 8 Plates, took an afternoon to drill and tap, used two sizes of drill 5 mm and tapping size. Hard work but keep the pressure on and change the bit as soon as it starts to rub.

Steve