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  1. #1
    Armedsask is offline Aluminum
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    Default NPT thread dims? Edit: Chart Added

    I recently had to do a quick one off job cutting some external 1 1/4" NPT threads in some plastic. Rather than getting our programmer to do it offline, I figured I can just hand write a simple program at the machine.

    Since it was plastic, I figured a quick turning path to produce the taper, and then thread it. I then spent an hour scratching my head and trying to calculate what diameters to turn the material to and what coordinates to program the threading too. The Machinery's Handbook gave me pitch diameters and I faked it from there until it fit since it wasn't a critical part.

    It got me thinking, there must be an easier way to figure this out. How do you guys do it? It's there a chart our there or formula I can use to figure out my programing points? I hate spending an hour doing calculations just to cut some simple pipe threads. All our pipe thread is usually programmed offline so I've never really had to do with it before.

    Any help is greatly appreciated.
    Last edited by Armedsask; 07-11-2011 at 09:02 AM.

  2. #2
    SeymourDumore is online now Diamond
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    Default

    One of the best money ever spent is this piece of software:

    ThreadPal

    If it has to do with threads, you will get it exactly!

  3. #3
    Heavey Metal is offline Titanium
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    Default

    +1 on thread pal. You can eaven change the size wires and figures it for you.

  4. #4
    Armedsask is offline Aluminum
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    Default

    I downloaded the trial verison of Threadpal. Great little program but I'm not paying $100 for a program I'll only use once or twice.

    I drew up a little diagram in Solidworks and I'm just punching in the numbers and making up a chart. So far my numbers match up with the Threadpal, so I'll just do it that way.

    I'll post the chart when I have it done so others can use it.

  5. #5
    SeymourDumore is online now Diamond
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    Default

    Quote Originally Posted by Armedsask View Post
    I downloaded the trial verison of Threadpal. Great little program but I'm not paying $100 for a program I'll only use once or twice.

    Suit yourself.
    But when the inspector comes calling with a thread dim being out a few tenths that you didn't even know about, I bet Threadpal becomes wicked cheap in comparison.

  6. #6
    Armedsask is offline Aluminum
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    Default

    Like I said in my initial post, this is for jobs that are quick and dirty one offs, like some guy just wanting pipe threads cut for some project. Tolerance is checked with the corresponding fitting, not a gauge.

    There is no inspector for what I'll be using this for.

    The following chart was created using the data from the Machinery's Handbook. The only numbers I came up with were the Major Diameter at Face (D2), Minor Diameter at Face (D3), and Length of Taper (L2). These were done by drawing the pipe in Solidworks and plugging in the different numbers.

    I make no guarantees as to the accuracy of the following chart. Use at your own risk.

    Last edited by Armedsask; 07-11-2011 at 06:55 AM.

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