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radiator tapping

mike jones_2mike jones_2 Member Posts: 92
is it ok to tap a new steam vent hole in a old cast iron radiator


  • Charlie from wmassCharlie from wmass Member Posts: 4,158
    depends on 3 things

    1- skill of person doing the tapping

    2- condition of radiator

    3- thickness of radiator where you want to tap it.

    Why do you need to tap it? Maybe there is another action that will bring better results.
    Cost is what you spend , value is what you get.

    cell # 413-841-6726
  • mike jones_2mike jones_2 Member Posts: 92
    radiator tapping

    Thanks Charles, the rad is in good shape, probly 1950's age so not super thick or tall.

    Someone plugged the normal vent tap half way down the radiator with something like epoxy and put the vent up hi on the rad with a bushing where the top side nut goes so the rad doesn't get hot enough and it is a cold northern room with a gorton d on it.  we tried all size gortons. 

    We can't torch the epoxy out, just drilled through it so we need to re-tap the hole or somehow get to the original threads for the new vent placement while we plug the top bushing hole.  or we could try to drill and tap elsewhere on the proper height of the cast iron and pray it doesn't crack.  we have the hanson 1/8 tap npt but that calls for a 5/16 drill bit which seems to thick.  thanks for your help!
  • Removing the Epoxy

    Hi- I would just use the tap to chase the epoxy out of the old hole threads.

    The 5/16 bit is actually just slightly undersized for a 1/8 -27 pipe tap so you should be okay there. I'd start with a smaller drill and drill a pilot hole in just the epoxy in the hole center and then take my time using a series of slightly bigger drills ( up to the 5/16)  to work the epoxy out. -possibly by just by chucking up each drill and turning it by hand until you have a large enough hole to engage the tap. Just be patient and take your time and carefully clean out the threads.

    If you're having problems with getting the air out of the radiator, you might want to use two vents - one in the "epoxy" threaded hole and one in the present location-at the top of the radiator.

    - Rod
  • Charlie from wmassCharlie from wmass Member Posts: 4,158
    Do what Rod said

    I would try with a properly located vent first and put a brass plug in the top vent hole. The threads may be gone in the lower hole, hence the epoxy. if this is the case then get an 1/8" close nipple, an 1/8" coupling, and some JB weld. you will need to epoxy the nipple into the radiator. Then you can thread you vent into the coupling. It is not ideal but it is cheaper than a new radiator and will function better with a proper height on the vent.
    Cost is what you spend , value is what you get.

    cell # 413-841-6726
  • mike jones_2mike jones_2 Member Posts: 92
    radiator vent tapping

    thanks that sounds perfect.  I guess we will put a level on the hand drill and use some 3 in 1 oil then just take it slow.

    by the way i didn't know it was ok to use a high and low vent on the same side of the radi .sounds like if there is no weird vacuum effect that we would have nothing to lose

    thanks again
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