drilling and tapping c.i. radiator

jjbex

A friend asked about a problem at his niece's house. I am a licensed plumber with minimal hydronic experience. A bedroom radiator has a bleeder about 8" up on the rad, there is none at the top, like the rest of the rads in the house. The bottom 8" of the rad gets hot. The top 2/3 stays cold. I suggested drilling and tapping a 1/4" hole and installing a bleeder. Is my thinking correct? Any tips on this procedure?
Thanks,
Jeff.

Firedragon_4

Right on!

Only tricks I know are use a sharp bit and go slow. Same with the tap.

gerry gill

drill and tap

for 1/8th inch NPT

J.C.A._3

JJbex

Do yourself a favor and go find an old time mechanic. He'll be able to teach you how to tap cast iron. Straight holes are just the beginning. Tapping the brittle material take a "good feel", and plenty of both oil and patience.

Been there, done that, replaced a couple of end sections successfully too! Practice, practice, practice....before making an attempt. It will save lots of time and money. If you can't find an old radiator to practice on, try an old engine block at a THIN walled section.If you make a mistake on that, keep practicing cause that is what you'll be dealing with on most radiators.(Trust me please, I've cracked new ones by installing the 1/8th " plugs with less than a 1/4 grunt. If the facory didn't check, how can you?) Chris

bob young

the man is a master plumber, i am sure he is capable of drilling & tapping a radiator. it is a task for a first year apprentice.threading and tapping are part of what he is a master of.

jjbex

drilling and tapping

I have drilled and tapped Schedule 80 pvc, when doing water parks. In my area c.i. isn't used in new construction. The only hydronics I have done is install baseboard. Most hydronic heat around here, which isn't much, is radiant. I do appreciate the tip about practicing on an old rad or engine block first. What kind of bit should I use? Carbide?


Cheers, Jeff.

Doug Wagoner

Use a regular drill bit.

Gray cast iron machines easily. Drill straight without wobble and tap the same way with cutting oil. I would tap for 1/8" pipe size. No need to go any larger. There should be a "boss" (a thicker part of the casting) near the top of the rad specifically for tapping in a bleed port.

Carl PE

If you've got a nice flat spot

on top of the radiator, go rent a magnetic base drill. use plenty of oil on the bit while you're drilling. go slow and easy.

when you've got the hole drilled, swap the drill bit for a center punch.

the tap should have a little divot in the top. use the drill/punch to apply light pressure to the tap while you turn it. this will keep you aimed straight.

again, go slow and easy. back the tap out about every half-turn, clean the chips, and re-oil it. if you get in a hurry and break off the tap, you're hosed.