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Drilling out stuck air vent plug on steam radiator

branimal Member Posts: 120
I've got a one way steam system and the prior owner of my building was using the top air vent hole to vent. I want to use the lower steam air vent but the plug in there isn't coming out.

I tried using a impact driver (not an impact wrench) to remove the plug. It's just stripping the screw head. Even if I could borrow an impact wrench I dont think it will work b/c the slotted plug is recessed I won't be able to get a flat head bit in there.

I think I've read that I need to drill it out. And rethread it.

Should I start with a small bit and make a starter hole, and then come back with an 11/32" bit (I think that's the correct size)?

I have a 1/8" 27 NPT HSS tap one hand.


    HVACNUT Member Posts: 3,797
    Are you trying use the plug with the scrape on it? I'm not sure but that might be too low. Better wait for a steam pro. 
    If it is ok, you'll need a tap and die tool.
    Always start with a small drill bit and gradually increase in size until it's the size needed to tap.
    I use a little Zoom Spout oiler so I don't burn up the bits.
    An EZ Out bit might work as well. 

    EBEBRATT-Ed Member Posts: 8,519
    That's going to be difficult. You need to center punch the exact center and that will be difficult with the slotted plug.

    If you don't get it centered exactly you may end up with an oblong hole.

    If it was me I would use the vent hole you already have.

    If you drill that one out be prepared to drill it out to 1/4" npt to be able to drill out the oblong and put a 1/4 x 1/8 bushing in the radiator
  • Steamhead
    Steamhead Member Posts: 14,326
    That hole location is right for a steam air vent in that particular radiator.

    Start with a small bit, drilling gently in the middle of the plug. Work your way up. Go slowly and pay particular attention to centering the hole. When you get most of the way to the edge of the plug, try an EZ-Out- you may be able to unscrew the remainder.
    All Steamed Up, Inc.
    "Reducing our country's energy consumption, one system at a time"
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  • branimal
    branimal Member Posts: 120
    I think the difficult part of drilling out the plug is centering the first hole I drill. I could center punch it as Ed mentioned.

    I have tried removing a broken off vent nipple with a nipple extractor before and cracked the radiator. I imagine getting a center drilled plug out is going to be way tougher.

    The only success I've had removing a plug was using an impact wrench with ground down slotted bit. The plug was the type that protrudes from the radiator about 1/4". I used a cutting disc on the plug and cut a slot for it. She came right out.

    Because the plug pictured above is flush with the radiator body, I'd need to get a good fitting slotted impact bit. Maybe a small diameter dremel cutoff wheel could help deepen the slot. The slot is just a hair under 3/8". So a 5/16" slot impact bit might work.

  • Grallert
    Grallert Member Posts: 491
    Get yourself some left hand twist drills run your drill in reverse. that plug might just come out while drilling. go slowly and be careful. If drilling doesn't spin it out carefully pick the remaining bits out.
  • mattmia2
    mattmia2 Member Posts: 2,652
    one you are almost up to the threads you might be able to cut a wedge out of it with a tiny reciprocating saw blade by hand and a tiny cold chisel.

    real cutting oil will work a lot better than general purpose oil, it has extreme pressure components that regular mineral oil does not.

  • branimal
    branimal Member Posts: 120
    Grallert said:

    Get yourself some left hand twist drills run your drill in reverse. that plug might just come out while drilling. go slowly and be careful. If drilling doesn't spin it out carefully pick the remaining bits out.

    Grallert you've told me to use these left hand twist drills a few months ago and of course I didn't listen and cracked a radiator using a nipple extractor. I'm going to buy 'em this time around.

    Is there a product you like? This seems to get good reviews.

  • Grallert
    Grallert Member Posts: 491
    Those should work. I use high speed steel, just what I have. Go slow and be patient. There are few things worse than breaking off a drill bit in the material. Get a good center punch that will guide your drilling. Don't be afraid to use a bit of heat and penetratingly oil with an easy out once you get most of the plug out if you need. In fact it wouldn't hurt to use a bit of heat and oil in the threads while you drill. It would be nice if this were an exact science but it's not LOL. good luck.
  • branimal
    branimal Member Posts: 120
    I going to order a better set from HD.  A lot of crap reviews on the set I posted earlier. My rad plug is effectively welded in there.

     I can see many uses for left hand twist drills.  

    So I’m kind of in a rush to heat up my workspace in brooklyn nyc.  I’m getting a hardwood flooring delivery in a few days.  And I want to get the space to 70 degrees.

    If I temporarily install the incorrectly vented rad, will it give me some heat?

  • mattmia2
    mattmia2 Member Posts: 2,652
    It will definitely work with the vent in the upper tap, it just may not all get hot because the steam may hit the vent ant close it before most of the air is vented out of the radiator, so it might be more like half or 3/4 heats. you could also drill and tap another hole somewhere near the plugged hole.
  • branimal
    branimal Member Posts: 120
    3/4 heat works.  Thanks
  • HomerJSmith
    HomerJSmith Member Posts: 1,196
    Why not try PB Blaster. Tap the plug with a hammer apply Blaster and tap more, apply more, tap more etc, then try an impact hammer, but don't go crazy with the power of the taping. Lite tapping over a period of time is better. You can always drill it out later.
  • kflory
    kflory Member Posts: 15
    I'd think that a broken bolt extractor kit would work well on that...
  • colinbarry
    colinbarry Member Posts: 11
    Another option... I've pulled a 1/8" plug out of a radiator like that by welding a nut to it and using a socket wrench to get it out.
  • HomerJSmith
    HomerJSmith Member Posts: 1,196
    edited February 27
    I should add to my previous post how to use the impact hammer. After spraying the plug with PB Blaster or CTC Knockem Loose take the impact hammer and put it on tighten so as to tighten the plug and tap lightly then put the impact hammer on loosen and tap the plug lightly. Repeat this a number of times. Don't rush it. Light taping is best. It takes time to loosen the plug. Don't rush it.

    You might want to heat the outside of the boss and go thru the procedure again. Everyone wants to just unscrew it which strips the plug or cracks the boss. Once it is out, chase the threads with a pipe tap.

    If you have no luck, the reverse drill with a screw extractor is the next step.
  • SteamingatMohawk
    SteamingatMohawk Member Posts: 390
    I have had to destructively remove remnants like plugs and parts of a male pipe end from a fitting. My process is to carefully drill a hole as close to the center as possible, then use slightly larger bits to enlarge the hole until I can use a saw blade (usually by hand) or a file (triangular or jewelers/needle no more than about 6 inches long) to cut to the threads in the base metal of the fitting or radiator. Once I have as small a remaining connection I try to tap on each side of the filed slot to break the metal. Once it is broken, the remnant may be able to be worked by tapping and using a punch to try to rotate/loosen it. If necessary, I make a second groove so a small piece can be removed, if cutting just one groove doesn’t work. It’s a tedious process, but if you are sufficiently lucky and careful, you can split the remnant and it will come out. Hopefully, there will be little to no damage to the base metal fitting or radiator. Use heat or PB Blaster too, carefully…you don’t want a fire.
    EBEBRATT-Ed Member Posts: 8,519

    I agree with your method most of us have had to do that. 1/8" plug is pretty small not very easy
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