A am fortunate to have a large set of solid carbide twist drills and that is what I use for hardened steel drilling on my projects......when I cannot soften the item 1st and drill normally and then re-harden.
CAUTION>>>>>>>>>>>>>>>solid carbide drills are extremely hard.....and break VERY easily! Only use them in a firm, rigid, no-play drill press or milling machine!!!!!
Good luck with your holes. Mabe check locally for a high quality machine shop or tool & die shop that will do it for you. AND............guarantee their work!!!!!!!
banger
I lightly skimmed through most of the previous replies so pardon me if I offer a suggestion that's already been put forth.
Back when I was doing some work on my K31 rifle I wanted to drill some holes in the side of the reciever but the metal on the reciever must be made of kryptonite or something cause none of my expensive drill bits would even put a scratch on the surface. (I'm aware it's the bolt you're trying to drill into but it's metal none the less)
At one point I laid my reciever on my lap as I attempted to get a hole started with what I thought was the hardest drill bit I could buy. The cutting tip seemed to be catching at one point so I pushed down a bit harder only to have the searing hot drill bit slip over the side of the reciever and into my thigh. It went into my thigh about a half-inch before I was able to stop the downward momentum. That drill bit had gotten so hot from just spinning and spinning on the surface of my K31's reciever that when I drilled into my thigh it didn't even bleed. I think it cauterized the hole in my thigh as it was sinking in.
It took that episode of ignorance on my part before I inquired of some of the other home gunsmiths online about how to go about this. Several of the replies I got were similar to the ones posted here. Some suggested "Spot-Annealing" others suggested stuff that I can no longer remember but the suggestion I eventually used was the one that mentioned a certain type of drill bit called a "Hi-Rock" drill bit.
I'm not kidding. None of my better drill bits would even scratch the surface of the metal of my reciever. I bought one of the Hi-Rock drill bits in the size I needed and it cut through the hardened metal of my K31 reciveer like a sharp knife through hot butter. Then I had to tap the holes I'd drilled. That brought about another dilemma but, that's where the spot annealing came in. Anyway, if it hasn't already been suggested or if you haven't already tired it, you might look into buying a Hi-Rock drill bit.
HollowPoint
I've had luck making a water based drilling fluid with Ballistol
I Am Descended From Men Who Would Not Be Ruled
Fiat Justitia, Ruat Caelum
Carbide bit. High speed. Do-Drill from Brownell's or Tap Magic for cutting fluid. Job is best done in a mill, but a drill press will do in a pinch IF it has no runout in the spindle bearing. Carbide bits don't bend, they break. Good luck.
NRA Life 1992
My avatar is almost a dead ringer for my little buddy Chico. Six pounds of mean that thought he was a Pit Bull. Miss that little guy.
BP | Bronze Point | IMR | Improved Military Rifle | PTD | Pointed |
BR | Bench Rest | M | Magnum | RN | Round Nose |
BT | Boat Tail | PL | Power-Lokt | SP | Soft Point |
C | Compressed Charge | PR | Primer | SPCL | Soft Point "Core-Lokt" |
HP | Hollow Point | PSPCL | Pointed Soft Point "Core Lokt" | C.O.L. | Cartridge Overall Length |
PSP | Pointed Soft Point | Spz | Spitzer Point | SBT | Spitzer Boat Tail |
LRN | Lead Round Nose | LWC | Lead Wad Cutter | LSWC | Lead Semi Wad Cutter |
GC | Gas Check |