Drilling 6A cryo stainless

[Larry L]

Just like it says. I have a knife blank that I need to drill a hole in for a 1/4" pin and nothing I have will hardly scratch this thing. It's 6A high carbon stainless that has been thru the cryo treatment. I've expanded existing holes before with a carbide bit in the drill press but I can't get anything even started on a new hole. I've tried carbide, titanium, and cobalt drill bits with zero results. I've also used much smaller bits as I know how to get the hole bigger. I'm using cutting oil too. So besides shooting a hole in it, how do you drill this stuff?

[Joel]

What speed are you drilling at?  When I use a pure carbide bit(spade tipped...twist don't work) I use the drill presses highest speed, which is around 4,000 rpm..and a lot of oil.  If you don't mind a hole a bit larger than 1/4 inch, I also get by with 1/4 inch glass drills( Lowe's) at around 1800 rpm, and a lot of oil.  Since 6A is the Japanese version of 440A with a bit of vanadium thrown in, it should be fairly easy to drill compared to the CPM154CM I use.  Also, what thickness is your steel?  Too thick and even carbides might not work.

[Larry L]

I've been using the slowest speed on the drill press which is 630 rpms. I stepped it up to 1800 but it didn't change anything with the carbide bits I have. I'll probably go by Lowes this afternoon and try one of their glass bits. Looked at them yesterday and considering the price shoulda pick a couple up. The knife blade is a little more than 3/16 thick (.20). I've drill out existing holes to get the right size for the pins I like to use but this particular blank doesn't have any in the right location. Seems to be a major difference between new hole and drilling out existing with this steel. I'm mostly a wood kinda guy....as if ya couldn't tell.


Thanks for the info. Doesn't seem to be many folks have a clue how to work with this stuff as I've Googled this a few times with next to no info.

[Victor3]

 One thing you might try is to put a steel dowel pin in the chuck, run it at high RPM and bring it down on the spot you want to drill. You have to bear down on it hard but it should heat and thus anneal the spot (it will turn blue when it's hot enough) so that it can be drilled. I've drilled through files using this method.
 
 Just be careful not to weld the pin to the blade. 

[Joel]

Yeah, basically what happens when I'm drilling hardened stainless is the spot turns red hot before the drill will penetrate;  until that happens...nothing.  Thing is regular drills can't seem to handle that heat level, while carbide or carbide tipped does. 

[Larry L]

Thanks for the info. I finally got thru it. I bought a diamond tipped bit in 1/8" from the closeout bin at Harbor Freight. It didn't cut it either but it got hot real quick. So I used some aluminum strips to act as a heat sink, let it get hot and then it got a grip and went right on thru. Using a masonry drill of the right size to enlarge the holes was like normal- fairly easy.
Thanks for the help.

[Victor3]

Yeah, basically what happens when I'm drilling hardened stainless is the spot turns red hot before the drill will penetrate;  until that happens...nothing.  Thing is regular drills can't seem to handle that heat level, while carbide or carbide tipped does.

 That's the beauty of using a disposable "heater" (dowel pin) before going to the drill. The greater surface area on the pin's end (as opposed to a tiny drill point) heats the area faster. Once you anneal the spot with it, any quality high-speed steel drill bit usually does the job without damging it. Carbide may handle the heat better but the pressure required to create it will often chip the point before it starts cutting.

[Joel]

Makes sense.  Back when I used to make knives out of files, I'd anneal the tang and drill with regular drills.  Never thought of doing it that way.  Hopefully I'll never have to drill hardened again(right), but if I have to I'll try it that way( and save some money).