Ok so short version. I Ordered a Tru trac (eatons Posi unit) for a Jeep JK> The JK switched to 1/2" ring gear bolts about 3 years ago from the now typical 7/16 or the for ever typical 3/8's.
The norm is to just use a step bit or a basic 1/2" bit in a small press that I have. Takes about 1 min per hole max.
BUT NO! The F#&)($ Eaton Posi has the most hardened case of ANY carrier/Locker I have EVER seen! The arb, detroit (another eaton product), trac loc, grizzly, Zip, etc... ALL are easy to drill. some a tad bit more hard but nothing bad at all.
I Tried 4 different drill bits, even indexing up & a few different unit bits, nothing even scratched the surface. NOT ONE Shaving any of them.
SO I went to a end burr in air die grinder, my last resort tool. It got about 1/8" in to about 5 holes, it was throwing sparks everywhere, but working. But after 5 holes it was shot.
The next day I picked up 3 more of these end bore bits at 21$ ea. After getting home and having 2 of them fall appart after only getting about 1/5th the way finished and not one hole fully open, I went looking for help.
I got a great offer from Vanimal. But he was far...
I remembered a buddy out in Riverside (only about 30 miles from me) and that he had a full machine shop in a hanger on his property. Not just a small one but like a hanger lol. He is a pilot and machinist, so I called him.
I got out there with the carrier and he took about 20 min to get it perfectly (well with-in .001) if centered and true in a Bridge Port chuck that he has setup in a digital 3 axis.
And he tried a end mill bit. It instantly started chipping apart a bit that he would use on anything else he does typically. He machines axles for tone rings (D44 swap in to XJ ABS rears), and wheels for hub conversions, etc. He opened a brand new end mill, and same thing.
SO I LUCKILY brought the one last new end burr and told him this is carbide and maybe this can work, he said well never had to try something like that and with only a 1/4" shank was not happy to have to try it, but he would.
After about 4 min per hole, it all worked out.
NOW WTF EATON! Why would you make a posi case that hard, when the detroit is not even close to the same hardness and more abused. Ugg...
Pictures..
OH and anyone that needs any Quality jeep work or machine work, he is for hire he said.