driling and tapping hardend steel

I want to drill my crank and tap so I can accommodate a M12 bolt to add a voyager 1300 rotor. I ordered the drill bit and tap. So I started to drill and not really making progress at all.This is some hard stuff.What kind of drill bit works on this stuff.I'm a newbie at this stuff and btw this is being done on a spare engine that I plan on rebuilding.I was thinking of purchasing a Voyager 1300 crank in the future,thanks.

I would suggest you spend the money on a Cobalt drill bit and also get yourself a bottle of lithium based cutting fluid (looks like green paste) The cobalt bit is tougher than hardened steel and the lithium based cutting paste (fluid) is the best I know of for drilling tapping tough material. You'll want to drill at a very low rpm and a lot of pressure otherwise you'll take the temper out of the drill bit and case harden the crankshaft with the heat generated. Try to judge the pressure you're applying by keeping the cutting paste from smoking.
Any other machinists out there care to chime in?

Hi Kenny,

Pretty sure that the usual order of processes is to machine a part and then heat treat it. I'm not sure you can do what your want without annealing the part first then machining it and then retempering it. I'm also pretty sure that there's a big risk that the heat treating will allow some internal stresses to be relieved resulting in a crooked part.

Wish I could offer you more.

Bill

KQZ you are correct. Standard process for building a crank would be to machine the part and then heat treat. Rework usually requires normalizing the part, reworking, machining and then heat treating. For a crank the heat treating is accomplished just prior to finish grinding the journals.
Cranks are made of a ductile iron which suggests a soft material. After rough machining they are usually nitriled to case harden the areas of the main and crank journals, then finish ground. Quite often if you carefully cut through the case hardening you can rework the base material which in this case should work.

I am a Fitter by trade and have done a lot of machining work. I would not even think of doing what you want to do unless the crank was in a lathe and I had a tungsten drill bit and even then I would be very doubtful of being able to tap a thread because the centre of the shaft wont be hardened but will be VERY tough steel.

This topic brings up old memories for me. I spent 30 years working in a nuclear power plant in Pickering Ontario as a machinist fitter and pipefitter welder. Thinking about the cutting fluid we used(the green stuff) I had to rummage through the old brain and came up with the name Anchorlube. checked out on the internet and yes that's what it was. I remember doing a lot of testing on cutting fluids for tapping/cutting threads and the best product we could find without a doubt was this Anchorlube G-771 and in the nuclear industry we played with a lot of unique materials the toughest being Zircoloy and you couldn't touch that stuff with a tool without using this Anchorlube. Thanks guys for making me use the old brain again. I love it!!