ARGGH! My drill bits are getting ruined when DRILLING GAS BLOCKS

We've all been there- you pull out a shiny new cobalt bit to drill the pins on a barrel component, and the bit just won't cut to save its life.  You put oil on in an attempt to help, and instead you smoke out the room and still have a roached bit.  What's going on?!?!?!?!

The reason for the drill bit un-aliving itself is that the nitride coating on the component (our gas blocks for example) is harder than the cobalt/steel alloy of the bit.  The common outcome is that the drill bit loses the fight and gets hot, which makes the steel soft, which makes it turn into a ball instead of a rotating knife.  

The answer is to use something harder- carbide!

This endmill (MCMASTER 29605A21) is super for two jobs.  The first is in cutting through the .001" thick nitride layer.  The second is for pin and welds, because it square cuts on the bottom and lets the pin get a really good bite.  For this job, come down very slowly into the work with a high rpm (On a bridgeport we use the lowest gear belt setting and full VFD), and just cut until you clean up the black into bright metal and you feel the endmill start really biting into the steel- when you're cutting the nitride it'll feel like nothings happening- again go slow!  The carbide is much, much harder than the steel and will shatter if you go too fast.  Definitely wear your eye protection!

Once you get through the nitride, STOP.  You don't wanna do the full cut with the endmill.

Next, switch over to a .113 drill (MCMASTER 28765A813) and keep cutting all the way through the part, with the same speed as above.

Finally, ream to .116 inches at about half that RPM (if you have a VFD) with this reamer: (MCMASTER 8803A237)

Here are the pins we use (MCMASTER 91595A112).

Note that this recipe (above) won't work for commie pins.  Europe and the US have different systems for press fitting parts.  The commie pins are oversized, and they drill undersized to get the interference.  In the US the pins easily available are on size, and you ream undersized to make the press.  You're not actually getting a .0015 interference fit with the above- the block distorts very, very slightly to allow the press.