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AN fittings

Discussion in 'The Hokey Ass Message Board' started by bandit14569, Feb 28, 2013.

  1. bandit14569
    Joined: Jul 18, 2011
    Posts: 69

    bandit14569
    Member

    Need to know how to measure AN (army/navy) fittings to determine what size they are. I need a new set of front brake line and there either 3AN or 4AN. Is the hole of the fitting,outter thread measured, or what?
     
  2. ftroop
    Joined: Sep 22, 2006
    Posts: 343

    ftroop
    Member
    from Detroit

    Brakes are typically -3
     
  3. JEM
    Joined: Feb 6, 2007
    Posts: 1,041

    JEM
    Member

    It's the OD of the tube that fits through the nut and sleeve, in 16ths of an inch.

    It'd be very rare for a brake system at the wheel to be anything but -3. If you've got a 3/16 brake tube (typical) and the tube nut takes a 7/16 wrench then it's -3.

    In some rare cases at the MC it might be -4
     
  4. bandit14569
    Joined: Jul 18, 2011
    Posts: 69

    bandit14569
    Member

    How is outter tube measured, calipers, micrometer, milimeters,inch scale?
     
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  5. JeffB2
    Joined: Dec 18, 2006
    Posts: 8,266

    JeffB2
    Member
    from Phoenix,AZ

  6. oj
    Joined: Jul 27, 2008
    Posts: 6,247

    oj
    Member

    Most drums brakes i have seen take a 1/4" line, or -4AN; most disc brakes i have seen take 3/16ths or -3AN. Wheel cylinders need volume to operate so the larger line.
    You can use -4 for either - i have seen some fords with -3 rear drum brakes but i wouldn't copy it.
     
  7. JEM
    Joined: Feb 6, 2007
    Posts: 1,041

    JEM
    Member

    Curious, I can't think of a single drum brake I've ever worked on that had 1/4in hard lines at the wheel, but admittedly my exposure to prewar stuff is thin.

    I just (as in this morning) wrenched the hoses off a set of '37 Chevy Huck drums that will be going on the pseudo-Brooklands-roadster project, and they had 3/16in SAE tube nut seats in 'em. All the '50s and '60s Fords I've ever wrenched on had 3/16 hard lines.

    The only place I've ever seen 1/4in hard lines was from master cylinder to junction block on GM product, and I think the only reason GM did that was so that some assembly-line worker didn't figure out a way to screw the wrong line into the wrong port.

    I'm prepared to be educated to the contrary, but that's what I've seen.
     
  8. JEM
    Joined: Feb 6, 2007
    Posts: 1,041

    JEM
    Member

    A caliper will be more than accurate enough. The tube sizes are (for what you care about) in 1/16in steps.

    In the modern world 3/16in tube is sometimes called 4.75mm but it's the same stuff. Some late production vehicles have an epoxy anti-corrosion coating on it but if it's less than 1/4in OD then the tube inside is 3/16in.
     
  9. Ghost of ElMirage
    Joined: Mar 18, 2007
    Posts: 758

    Ghost of ElMirage
    Member

    It's a 3AN . The smallest we use on our aircraft is 4AN which takes a 9/16 wrench and that is giant for an automotive brake system.
     
  10. bandit14569
    Joined: Jul 18, 2011
    Posts: 69

    bandit14569
    Member

    OK..........the charts and all the info was great, been wondering for awhile....Thanks
     
  11. Drive Em
    Joined: Aug 25, 2006
    Posts: 1,748

    Drive Em
    Member

    I bought a huge selection of #4 AN fittings at a government auction about 20 years ago. Thete are hundreds of unions, nuts and sleeves, bulkhead 90 degree fittings as well as bulkhead tees. I have plumbed several dozen brake systems in #4 and it works awesome.
     
  12. Ghost of ElMirage
    Joined: Mar 18, 2007
    Posts: 758

    Ghost of ElMirage
    Member

    Ya 4AN will work it's just overkill
     

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