cleaning/dressing old pipe threads

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by gardner, May 11, 2009.

  1. gardner

    gardner DIY Senior Member

    Messages:
    217
    Location:
    Ontario
    I have a somewhat grotty old 3/4 threaded hub on a galvanized steel fitting and I need to thread a new 3/4 brass fitting into it. The old threads are not particularly nice, but they are likely serviceable. Is there a standard procedure for cleaning and dressing an old rusty, putty-encrusted fitting to take a new fitting and make a good seal?

    I was thinking of getting a 3/4 black pipe nipple, cutting a slot across the threads (like on a self tapping screw) with a grinder and using this to run into the old hub to clean up the rust and crust. Kind of a home made chasing tap. Is there a better way?
    Last edited: May 11, 2009
  2. nhmaster

    nhmaster Master Plumber

    Messages:
    3,189
    Location:
    S. Maine
    Lotta work when you could just bust out the wire brush. If the threads are bad you need a 3/4 npt die to chase them.
  3. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,351
    Location:
    Yakima WA
    You might find a set of pipe dies at a tool rental store. Shouldn't cost too much for half a day. If you were in Yakima, I'd loan you a 3/4" die.:D
  4. Nate R

    Nate R New Member

    Messages:
    472
    Location:
    Milwaukee, WI
    Doesn't he need a 3/4" tap? :D
  5. nhmaster

    nhmaster Master Plumber

    Messages:
    3,189
    Location:
    S. Maine
    I have a somewhat grotty old 3/4 threaded hub on a galvanized steel fitting and I need to thread a new 3/4 brass fitting into it.


    Yep. :mad:

    The disadvantage of speed reading :D
  6. gardner

    gardner DIY Senior Member

    Messages:
    217
    Location:
    Ontario
    Thanks all. I'm sure the hub won't be so bad I need to run a real tap into it. I expect I can get by with a wire brush. This is a cottage/camp project and I am trying to plan ahead for what I may need when I get there and start working on it, so that's what got me going on pre-fabbing a low budget tool, just in case.

    Besides the bogus threaded 3/4 fitting on my pump to fix, I also have a couple of burst copper lines to take care of, as well as correcting the pitch of those lines and adding a drain to avoid water staying in the lines next year.
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