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Thread: 1/4 NPT External thread program

  1. #1

    Default 1/4 NPT External thread program

    Can someone help me with programming 1/4 npt external using G76 (fanuc O-T). I do not know what values to put in for the thread dimensions. Thanks!

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  2. #2
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    .54 dia start point with 1.75deg per side. Is it help.

    The best way to learn is trial error.


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    I'm threading 1/4 npt threads on a fanuc ot controled cnc lathe. Can anyone give me some help on the second line of info using G76?



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    Lead is 18 threads per inch, taper is 0.0625" per inch diameter measure, finish diameter is around 0.56", length is around 1/2".

    An open mind is a virtue...so long as all the common sense has not leaked out.


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    Thread ending point figured at center of 16ER 18 NPT insert and L4 dimension from Machinery's Handbook.

    Finish turn .016R insert
    X.3768Z0
    G3X.4065Z-.0062R.021
    G1X.5249Z-.0653
    X.54Z-.3077
    Z-?

    Finish turn .031R insert
    X.3468Z0
    G3X.3977Z-.0105R.036
    G1X.5245Z-.0739
    X.54Z-.3224
    Z-?

    Thread 1/4-18 NPT external
    X.58Z.3
    G76P000155Q30
    G76X.467Z-.634P444Q150R-.0291F.05556

    Changing starting point or ending point will require R to be modified. R=tan(1+47/60)*(start point + end point) unless both points are the same sign, in which case you would subtract them.

    Single block G76
    X.58Z.3
    G76X.467Z-.634I-.0291K.0444D150F.0556A50.

    Did one of these work okay for you?



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    Apparently my examples didn't work. What did you finally wind up with?



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