Advice on drilling through hardened steel?

[Kevin Sevcik]

do you need all the strength that comes with the hardness? I mean. if you don't actually need the extra strength, then just hit it with a torch until it's cherry red, hold it there for a few minutes, and then let it air cool. That should kill the heat treatment of most steels unless it's one of the air quenching varieties.

[IndyStef]

Dependes on how hard hard is.
Properly hardened high carbon streel, like tool steel for punches and dies - forget it, you won't even sratch it with a regular HSS bit, no matter what coating. And hard metal bits, or carbide bits won't help you much, either.
Surface hardened by carbonizing, or induction treated - with a hard metal tipped bit, or carbide, you might be lucky. Once you are through the surface, things get better.
Tempered steel - depends on the treatment it got, but generally coated HSS or carbide will do the trick - just a lot slower than on Al or mild steel.
Unfortunately, the use of the word 'hardened' is a bit blury in the English language - so you might just talk about a high tensile alloy, or a tough stainless steel. In that case: coolant is the answer. Increases the life of your drill bit a lot. Also - drill presses are not used in the same way as hole punches! Apply force, but not so much that the machine twists and bends. And keep the bits sharp by re-grinding them.

Hope that helps ... some rambling of a German toolmaker and mech. eng. .....

Stef

[Greg Perkins]

are yuor drive shafts out of hardened steel?

[maclaren]

It's all about the carbide drill bits. To do the drilling correctly you first must figure out exactly what you are drilling. Then you look in your machinists handbook(noshop is complete without one) for speeds and feeds. Then use a milling machine or high quality drill press. Use flood coolant. The coolant type is important for a good finish and keeping the drill bit cool. You can also find what type of coolant to use in your machinists handbook. If your bit heats up then it loses it hardness which makes it dull extremely quickly. Drilling is a battle of hardness and sharpness the hardest and the sharpest wins. You want the drill bit to win . You can purchase carbide drill bits at Enco or from MSC industrial supply co.

The moral of the story try and put hole in hardened steel before it's hard the harden it. Because there is no way to BS machining hardened steel.