By the way,..run the drill slow and keep a dab of dark thread cutting oil on it when you're drilling.
Run it too fast and it'll work harden the steel you're trying to drill through. D2 is especially tough to work.
What he said. Try drilling no faster that 50 SFPM. * Also try hand sharpening them to around 118 Deg included angle and splitting the point. You can sharpen a drill by hand better than a drill dr will do it. If the chips are blue you are turning the drill too fast.
* SFPM = Surface Feet Per Minute. To calculate SFPM it is the recommended cutting speed times four divided by the diameter. That would be in this case SFPM = 50 times four /divided by drill diameter. Say for a 1/4" drill it would be 50X4/.25 = 200 RPM.
I'm not familiar with the formula, but as written it is equal to 800 RPM.
Just goes to prove you don't have to be smart to be a machinist.
Thanks for keeping me straight. The formula is just a rule of thumb. It simplifies the math from using Pi to figure circumference of the drill. It works for any turning situation. When drilling or milling it is the diameter of the tool, when turning in a lathe you use the diameter of the piece being turned. It is not a hard and fast rule but it is a good place to start.
The recommended cutting speeds for many materials can be found in the Machineries Handbook. I took the 50 SFPM for D2 from memory. I am not a hundred percent sure that is right.
