re: Drilling angled holes in a cylinder

If it’s important enough to make a jig for, it would be simple enough to weld some tube with a matching ID to the your drill bit to a section of pipe with an ID matching the pipe OD you want to drill. Not hard to set angles, and the welds don’t have to be perfect to act as a drill guide. 

Or, you could make it out of wood. I envision a block of wood, drilled along the long axis with a large forstner bit to match the OD of pipe you want to drill, then split along that axis to give you a half round trough along the long axis. Then lay out your total angle across the top and cut some flats so your bit hits the wood at 90°, but is 30° off center (and 60° offset from each other). Then drill straight through the block to create drill guides. Clamp the block to your pipe, then lube up the holes and drill away. Two drill guides keep you from screwing up alignment of a second drilling operation, but one drill guide would certainly work…you just need to layout your angles on the work piece and line up the guide. 

Someone will come up with something simpler, but that’s what I got off the top of my head.