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how to thread a taper

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  • Circlip
    replied
    Yes, the O/P asked for a threaded taper as shown in Evans pikky, not to be confused with a tapered thread. A threaded taper must be cut with the thread at right angles to the taper, a tapered thread is first cut on a parallel bar and the taper then cut. In real terms, a threaded taper is a "Bastard" pitched thread, unless cut with a taper turning attachment.

    Regards Ian.
    Last edited by Circlip; 03-21-2011, 09:03 AM.

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  • duckman
    replied
    Why don't you use a connector thats what they are made for, no threading, no screwing, just heat the ends in some hot water and push together, done.

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  • Errol Groff
    replied
    I have scanned and posted the Taper and Threading chapter from the text we use at school. It can be found at:

    http://neme-s.org/Shaper%20Books/shaper_book_page.htm

    Scroll down to the link Tapers and Threading.

    Setup for taper threading is on the last page of the file.

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  • John Stevenson
    replied
    Yes that would work, well worth remembering.

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  • Evan
    replied
    Anything longer will leave you with a parallel trailing end which will be at the smaller diameter
    Just start over again on the smaller diameter making sure the threads are timed.

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  • John Stevenson
    replied
    Originally posted by Evan
    Like this:

    That will work but only if the length of the taper is equal to the width of the die insert.
    Anything longer will leave you with a parallel trailing end which will be at the smaller diameter.


    Still probably the quickest way to do short threads.

    Most taper threads are usually 1.5 x D in length so this teels you what the width of the die insert needs to be, if it's possible to get one that length.

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  • Oldbrock
    replied
    I have done it that way myself but rohat said he locked the carrage, that is what I was questioning. Peter

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  • Evan
    replied
    That is a threading die. You set it to the correct angle and then proceed as if single point threading. The back end starts cutting first. By the time you have advanced the depth so that the leading tooth is cutting to full depth the full taper is developed. It is no different in operation than single point threading.

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  • Oldbrock
    replied
    The chaser still has to move one pitch per revolution. Or are those anular grooves? Peter

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  • Evan
    replied
    Like this:

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  • Oldbrock
    replied
    Rohat, I've been machining for 60+ years and you totally lost me. How can you cut a thread if you lock the carrage down? Also how do you make the compound move the correct threads per inch. Peter, old fart turner from North Wales moved to the colonies

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  • wierdscience
    replied
    Like JC said the tool is set 90* to the pipe's axis.If using the tailstock offset method,set the compund to 28-1/2*IIRC and singlepoint as any other thread.Edited to clear brainfart

    Everything you need to know about thread specs and profiles.

    http://mdmetric.com/tech/threadtech.pdf
    Last edited by wierdscience; 03-19-2011, 10:06 PM.

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  • Boot
    replied
    Fishtail

    Yes you have to cut taper first and then use your fishtail to set the threading tool 90° to the taper. And yes the thread will diminish as you cut to the end of thread.
    Boot

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  • Boot
    replied
    Tapered pipe threading

    I did a lot of this type of threading. All the way up to 6" dia. It is done with a taper attachment on an engine lathe. The taper is as some one else said is 3/4" per foot. We used 11 1/2 thread per inch for most of the larger sizes we did. I don't recall what the 6" required. It was 20 yrs . ago. You can do it by shifting the tailstock over and holding part between centers when you do. You single tool thread it and use the compound set at 29 1/2 degrees. Advancing the compound a few thousands at at time and backing off at the end of thread with the crosslide and return in the crosslide to "0" to start again. that way you only advance on the compound. Watch Twobalcain on the You Tube site for threading example. You actually only cut on one side of the thread form doing it this way. Good luck . I wish I could show you on you engine lathe. Also use the thread dial on engine lathe. Simple to do.
    Boot

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  • Astronowanabe
    replied
    one way for pipe threads ...
    I do not know if they make left hand pipe threads

    http://bbs.homeshopmachinist.net/showthread.php?t=36866

    but the pipes you are joining usually have their threads one the outside not the inside in which case you would be wanting a female coupler ...
    maybe I need to go back and reread the question

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