tappping a new hole

humhead

in a cast iron steam radiator for a new vent hole.  What size drill bit do I use for a 1/8 tap?  I am installing a Burnham  radiant.  I need to install the vent on the right side of the radiator, and I can not remove the slotted plug.  Would it be wiser to drill out the plug. using an (easy-out)?  Any suggestions would be great. 

icesailor

Tapping Hole:

Before I tried drilling a new hole, I would try to get theslottedd plug out. I would drill a hole in the middle of the plug and carefully enlarge it. I use a Dremel Tool. They sell a carbide grinder bit that is around 1/8". Grind it carefully and try your screw extractor. Then run a 1/8" pipe tap through it.

Owen

Good Answer

He's right. Cast is a bummer to drill into. Slow, many bits, need to oil the bit, etc. Stress on the carefully part.

ChrisJ

stripped

I'm about to do some work on one of my rads as well.  The 1/8" hole is stripped so I'm planning on drilling it out some and tapping it for 1/4" and then installing a 1/4" to 1/8" nickel plated bushing.



I hope I can pull it off.

Dave in QCA

Drilling Cast Iron

When you drill cast iron, be patient.  Make sure you have a very sharp big, don't drill so fast that you burn up the bit.  It will take a while and it tends to wear out bits, but it's not that big of a deal.



I have seen many radiators that had to be drilled out, then bushed with a 1/4 x 1/8 bushing because the original thread were worn out and enlarged.  This is one reason that I never recommend turning a vent upside down as a means of turning a radiator on and off.  Ultimately, damage is likely to occur, especially if the vent turning is being done by the hands of a person who is not mechanically inclined.

ChrisJ

threads

Dave,

I noticed on most of my rads I only get around 2 MAYBE 3 turns on my vents before its tight.  Usually 1.5 turns it starts to feel snug then I go a half a turn to get it pointing upward. The threads appear to be in a decent shape.

This seems odd to me as usually you get a good 4 turns or so on an 1/8" pipe no?

I'm thinking about running an 1/8" tap through most of the threads to clean them up.  Maybe a bad idea?

Dave in QCA

good idea

If you aren't getting many turns, the threads are likely rusted or otherwise clogged up.  I agree with your idea.  I would clean them out with your 1/8 tap, clean off the threads on the vent, then reinstall the vent with a proper amount of teflon tape.

ChrisJ

tap type

Dave,



Would you recommend a "high speed steel" tap or a "carbon steel" tap for tapping radiators?  I'm asking only because I have to assume the HSS tap would hold up better tapping cast iron.