Drill and tap for vent in cast iron rad

Mad Dog

get a nice adjustable real tight on the sqaure stock of the tap, and give the whole thing a few nice taps as i make my first few turns - this way it grabs and goes in straight. mad dog

JM_2

Anyone have info

on the best way to drill and tap a cast iron radiator for a new steam vent? The radiator comes from a FHW system. It has a dimple for a vent about 1/3 from the bottom. What size bit should i use? What speed should i drill at? What type of tap should i use? Finally should i just bring it to a machine shop and have them do it? ( The radiator is not to big and i can move pretty easily)

Unknown

First things first.

About 5-10% of the time in my estimation, the old radiator can crack when you do this. Be gentle.

Buy a NPT pipe tap in 1/8". The drill size is usually written on the side of the tap. Use cutting oil on the bit. I do it right in the house, connected. Let no oil get inside the radiator. The drill should be fast. Tap it.

Put the right vent in it, and if the waterline becomes wildly bouncy, you got oil in it.

Noel

Eric Taylor_37

Pilot hole

Start with a smaller bit first, say 3/16" and then go with the finished size. The hardest part is getting the tap started straight. Use a new, sharp tap and go back and forth alot to break up the chips. Remember that the pipe tap is tapered! if you go too deep the hole will be too big. Its best to stop and check the threads often. You can always go deeper.

Eric