Drilling

Doubtful. Carbide drill bits are very hard, but fragile. Inconsistency in run out generally breaks them. You can sometimes get away with using a masonry bit, with a carbide tip soldered to an HSS drill blank, but masonry bits are not ground to cut steel, so in order for that to work you need to know how to grind them, and have a diamond or silicon carbide (green) wheel on your grinder. There are some brazed carbide drills out there that are meant for drilling hardened steel but I have never used them and can't recall their name.

I've had the best luck drilling hardened steel with Hi Roc straight flute bits, but like I said, either in a very solid, tight drill press or milling machine. You're almost guaranteed to break them with a hand drill.

Your best bet would be to try to spot anneal the areas you wish to drill. If that's not possible, then anneal and reheat treat after drilling. Unless you have a friend with a fast hole popper or a sinker edm. But if you did you probably wouldn't be asking.
 
FWIW when I need to drill through hardened steel I use a 4 flute carbide endmill, run fast, in the drill press or mill with light feed. Works fine, just let the bit establish the hole with little pressure, so it won't walk, then you can increase the feed a little.
 
As mentioned its not easy.
I use Strongarm Drillbits. They are a carbide insert type and are tough enough to use in a hand tool. They will put through a hole, but wont be highly accurate one hole to the next.
 
yes you can. you will need a decent carbide drill and a stable drill press. i do all my folder blades post heat treated, including rwl34, m390, w2, etc. personally i run at 900 rpm, and i prefer 90 degree drill bits.


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An untouched up carbide masonry bit with just an an arrow shaped carbide tip and a typical hand drill will eventually go through, but you will get an ugly hole and it's a PITA. It's definitely "the last refuge of the incompetent" (at least that was the case for me when I did it :-D ).

If at all possible drill before HT, buy a drill press and a proper carbide bit, or find a friend with proper tooling.
 
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