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Thread: Pipe threading on a lathe

  1. #1
    Join Date
    Jan 2008
    Location
    Mouldy, Or
    Posts
    395

    Default Pipe threading on a lathe

    Perhaps a known trick but as I (re)discovered it, I will pass it along
    threading pipe on a lathe is complicated by the fact the thread is on a cone
    with a 1 deg 47 minute taper, the options I read about were:
    1) Don't. Use a pipe threader, that is what they are for.
    2) offset tail stock and turn between centers
    3) back the cross slide off a certain number of thou per revolution

    well, my part is not a pipe and won't fit in the pipe threader
    I could turn between off set centers but it is a fiddley setup to get a dog on
    a short piece and then would have to set the taper up properly
    and restore the tailstock to center when done

    manually backing the cross slide off on the fly
    when there are already plenty of things to keep track of
    while threading a short section seems like inviting a problem
    especially if there are a number to do.

    the way I found was to use a jaw from the pipe threading tool
    as a form tool just as you would single point an untapered thread of the same pitch.
    Clamp the tool parallel with the face of the chuck
    and back it off & disengage the feed (in that order)
    when it just becomes fully engaged.

    --
    Tom C
    ... nice weather eh?

  2. #2
    Join Date
    Dec 2003
    Location
    Palo Alto, California
    Posts
    1,305

    Default

    Good going, schmarty! I have a pipe threading die set, and I'll try to remember this trick, you betcha.
    Cheers,

    Frank Ford
    HomeShopTech

  3. #3
    Join Date
    Aug 2006
    Location
    Beaverton, OR
    Posts
    7,184

    Default

    You missed the fourth option. Use a lathe with a taper attachment.

    Your technique here also works using taps as the cutting tool to cut the thread.

  4. #4
    Join Date
    Jul 2009
    Location
    Granite Falls, Washington
    Posts
    144

    Default

    Nice.

    I have a use for that TODAY

  5. #5
    Join Date
    Nov 2001
    Location
    Toledo, Ohio
    Posts
    9,098

    Default

    Good use of a threading die.

    While pipe threads are tapered, the stock is straight. Using the setover tailstock method will not produce the proper thread form. A taper attachment is about the only method of single pointing pipe thread. Backing off the compound will sort of work, but is a pretty iffy method unless leakage is not a problem.
    Jim H.

  6. #6
    Join Date
    Sep 2004
    Posts
    2,976

    Default Good Application of Brain matter Buddy

    I do all types of wacky threads and this pipe thread tip is going to become one of my No Pain No Brain setups. thanx for the idea.

  7. #7
    Join Date
    May 2002
    Location
    NL
    Posts
    1,390

    Default

    "Your technique here also works using taps as the cutting tool to cut the thread."

    ? going to try it in the am as I have 6 1.250 pipe to do
    for the son's girl friend's father...
    please visit my webpage:
    http://motorworks88.webs.com/

  8. #8
    Join Date
    Nov 2001
    Location
    Toledo, Ohio
    Posts
    9,098

    Default

    Quote Originally Posted by motorworks
    "Your technique here also works using taps as the cutting tool to cut the thread."
    That could be made to work with a bottoming tap for screw threads, but I would not be too sure about the applicability for pipe thread unless the tap is used the wrong way around. With pipe thread, the thread on the tap gets shallower the deeper the tap goes in. You would need to do some creative fixturing and grinding of the tap to get it to work if it would work at all.
    Jim H.

  9. #9
    Join Date
    Apr 2009
    Location
    Columbus Texas
    Posts
    683

    Default

    I was going to post a topic on the same thing. We changed out the die teeth on our Ridged 300. Will any die number work?

  10. #10
    Join Date
    Feb 2007
    Posts
    2,078

    Default

    The tap would have a right hand thread,but would be presenting the thread at backwards of its angle to the pipe being threaded. Maybe if you presented the tap so the cutting edge was presented very much downhill to the pipe,you could avoid most of the conflicting thread angle issue.

    An old book I read described how you could make a left hand tap by trapping a rt. hand tap in a steel hole,and screwing a blank tap in beside it,which would come out left hand.

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