[asid61]

For the CIM hole, the method I like is to drill with a 1/2" drill, then a 5/8" endmill, and finally a 3/4" endmill to finish the hole. This gives a solid fit, and using an endmill ensures that the hole is exactly where the DRO says it is.
For the bearing, I normally go for a 1/2" drill, then a 3/4" endmill, then a 1" endmill, and finish with a 1.125" endmill which gives a nice slip fit or tight fit on bearings. If you can't step up from 3/4" to 1" safely and don't want to have to use a 7/8" endmill, or if you want a press fit, then a boring head is your best bet. However, if properly designed you'll never need a press fit.
Using the template method mentioned above works for inaccurate parts, but I wouldn't do a gearbox. It's good for finishing a gearbox so it doesn't look or weigh all square and clunky.