Taking a short break so I thought I'd post this as I've not seen it posted before. There's a commercial jig/fixture offered these days, but I'm not about to spend $125 for one. I took a piece of hot rolled flat bar that was about 1 1/4" thick by 3" wide and squared it up. I made 'grasping' cuts on each side of the bottom for my vise to clamp on and then used them and surfaced the top side. I centered up on the 3" width and found an appropriate spot to drill the 1 1/8" 'clearance' hole. I then located a spot for the bolt hole. Clamp your recoil lug down so that it's over the 'clearance' hole. Dial it in using a centering indicator. Anyone who owns a vertical mill should have a centering indicator. It'll save a lot of time and insure you are centered over an existing 'hole', if you don't know here center is. "Open" the 1 1/16" hole in the recoil lug to the desired size using your adjustable boring head. Again, another tool anyone who owns a vertical mill should have. Both of these tools, the boring head & centering indicator, have a bunch of other uses besides this job. That commercially made fixture/jig has only ONE use, opening the hole on a recoil lug.