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Flare Nuts

What are the main differences between long neck and short neck flare nuts.


  • STEVEusaPA
    STEVEusaPA Member Posts: 6,506
    $ .40
    HVACNUTpecmsgRobert O'Brien
    EBEBRATT-Ed Member Posts: 15,524
    Short ones are sometimes easier to get on a piece of tubing that is bent. In most applications it doesn't matter which ones you use.

    The short forged flare nuts are considered a little more heavy duty and are usually used on refrigeration. Their are also some special ones with slots cut in the threads to make them frost free.
  • Bob Harper
    Bob Harper Member Posts: 1,035
    The Nat'l and Int'l gas and mechanical codes do not prescribe or prohibit either type. The TSSA in Canada allows only forged or short nuts. They do not allow milled or long nuts. The most important thing is to make a proper flare and don't over-torque it. If it doesn't seal, cut off the flare and re-make it. Also, per the Copper Tube Handbook no dope or PTFE( Teflon) on flares. Also, no corrosive soap bubble test solutions. They cause stress cracking of the base metal.