Success with tapping. I got in an AR15 buffer tube tap (1.1875" x 16 TPI) tap yesterday and gave it a whirl today. After machining the hole with a boring head to 1.125" it was time to tap it by hand. By centering the hole on the mill and using an 1/8" pin clamped in a collet pushing on the back of the tap to keep it centered I used a wrench to turn the tap. Overall I'm happy with the result and now I can begin applying it to other projects such as the Havoc adapter plates.