You need a tool called a pipe notcher to do it right. Like this one
Sync180 JR Tube Notcher
Then you attach a drill chuck to it. This allows you to center the hole and drill it straight.
Alternatively you can use a punch to create a dimple for the drill bit. Drill the first hole then insert the fitting and use the fitting guide the bit and proceed to drill the second hole.
Better yet use speed rail and save your self a headache and some weight.
If you were in the medford, or area I's help you out.