I'd still be inclined to use the drill something like that, if its worked already.
If it won't cut, nor would say a slim chainsaw file, (there's at least two common sizes)
Then a diamond file might be the ticket... I've never used those, but see them in the shops frequently.
That's if the hole just needs the teeniest amount opened up.
If those need a large opening, it might be worth revisiting the drill...
Did the bit cut any holes in them?
Have you tested the bit in mild steel to see if the bit was much good to start with?
I'd reckon those bits are fine, and just need a sharpen.
Recently had to drill large holes in some hardened steel, and bought a good few fancy cobalts for the job.
I didn't notice much difference between them and the HSS used after them to be honest.
The edge gets wiped out quick.
No point in looking for better bits IMO, the next level up is cobalt and will likely have a split point which won't serve any purpose for opening up a hole.
Some bits aren't sharp out of the box.
I'd try testing on some scrap to see if they were any good to start with..
Have a scrap piece of softer metal held down well, as if those brackets are setup for a pillar drill, then that is a good opportunity for an accident testing random bits on the fly.
Might be worth considering a different method than good screws for holding those clips down.
I wouldn't expect anyone to learn sharpening drills for something as little.
But if wanting to know anyway...
I've messed about with cutting angles and whatnot for a few days, in the last month, making stout washers for a machine from a lawnmower blade, had to scrap that idea as could only get the holes drilled so big.
I was expecting to find more info about this, thinking there was an additional technique
to grinding the heel away the reduced cutting angle for hard steels.
I was doing a lot of searching, but seemingly everyone does the same all over the world with the traditional grind, taking split points ut of the equation.
I reckon AvE's video is about as good as you will find, regarding technique used, the same technique as on the bench grinder.
Could be worth a quick try, to see if they might cut those brackets.
Tom
