I am trying to drill and tap my cam for a rear drive spud. I had a guy at a machine shop try to drill it out and he broke two drill bits and didn't even get very far. My cam is a roller cam and he thinks they have a special harden on them which prevent you from drilling them. Does anyone have any experience with drilling and tapping a roller cam? Thanks for the help.

Need a cobalt / nitride drill for any thing that hard.

Very slow, on a lathe, with lots of cutting fluid.

MHO, either call one of the engine builders, or send it back to the manufacturer, and let them do it, even if you get it drilled, I'd worry more about a broken tap, it ain't gonna tap any easier than it drills. Bob

Bob speaks the truth.

they are case hardend, the original cams are drilled & tapped before heat treat. if you can drill the cam and drill it straight after you cut the little counter bore the threading should be faily easy as the cores are easily tapped