Some tips I know;
You can drill or not drill a relief hole for the pipe tap's drill size, you're drilling into cast iron that has a fairly thin wall, it's not like you're drilling 1 inch deep. Assuming you're running an el-cheapo 118 degree buy it anywhere drill(s) - which is fine for the job. For cast iron, typically you want to "spoon" it out but since it's a one hole job it doesn't matter again how you go about it aslong as you got a semi decent tools.
Use of a center drill, spot drill is the correct way to put a "mark" for the drill to start on. I don't like hole punches personally. Most people probably dont even bother, again. it's one of those things that usually wont make much of a difference aslong as you're going in straight as possible.
Use an oil of some kind (ie. WD40) that'll keep the chips from sticking and keep the drill cool, you're good to go. Cutting oil is probably the best, but since you're only drilling 1 hole and it's not that deep, anything should work. I wouldn't use grease.
After you get through, there is probablly still small particles inside there. Vacuum, and/or a magnet will do the trick as you noted. The real smaller dust sized metal particles that might make it's way through probably wont hurt anything.
You can drill or not drill a relief hole for the pipe tap's drill size, you're drilling into cast iron that has a fairly thin wall, it's not like you're drilling 1 inch deep. Assuming you're running an el-cheapo 118 degree buy it anywhere drill(s) - which is fine for the job. For cast iron, typically you want to "spoon" it out but since it's a one hole job it doesn't matter again how you go about it aslong as you got a semi decent tools.
Use of a center drill, spot drill is the correct way to put a "mark" for the drill to start on. I don't like hole punches personally. Most people probably dont even bother, again. it's one of those things that usually wont make much of a difference aslong as you're going in straight as possible.
Use an oil of some kind (ie. WD40) that'll keep the chips from sticking and keep the drill cool, you're good to go. Cutting oil is probably the best, but since you're only drilling 1 hole and it's not that deep, anything should work. I wouldn't use grease.
After you get through, there is probablly still small particles inside there. Vacuum, and/or a magnet will do the trick as you noted. The real smaller dust sized metal particles that might make it's way through probably wont hurt anything.