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IndustryArena Forum > MetalWorking > General Metalwork Discussion > Thread Milling rules of Thumb
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  1. #1
    Join Date
    Apr 2010

    Question Thread Milling rules of Thumb

    Looking for anyone with experience thread milling smaller holes. Specifically 5/16-18 3B.


  2. #2
    Join Date
    Aug 2015

    Re: Thread Milling rules of Thumb

    5/16" isnt that small as far as threaded holes go.

    Climb milling gives you a better finish. Bottom to top for a right hand thread.

    For a 5/16-18 you have about 0.03" of thread depth per side. Try 5 passes with a 0.005" step-over and the last two passes at 0.0025".

  3. #3
    Join Date
    Jan 2015

    Re: Thread Milling rules of Thumb

    download Fusion360 its great for just about everything from Design to Manufacture and its like only 20 bucks a month . And does a great job posting a file for just about any machine easy to create a threadmill program

  4. #4

    Re: Thread Milling rules of Thumb

    Five passes??? That's nuts. One pass for fine threads and two passes for course. Especially on a size like this. (Note this will not be relevant to every single material out there.) Try to get used to programming thread milling in incremental. One small sub can do a hole at any location, as long as you start the tool typically, but not necessarily, centered above the hole. For the two pass version, just set up a different D address comp for each pass. Cut something around 70% of thread depth the fist pass and full the next. You most definitely will need thread gauges for thread milling, as you'll have no multi-million dollar tap company working for you to make things just right.

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