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    Registered kstrauss's Avatar
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    Default Thread milling questions

    I am new to thread milling. I need to cut internal and external 7/16-20 threads in Delrin. I have a Tormach 34694 thread mill. What should I use for DoC and feed and how do I calculate it? I have GWizard but I'm confused how to enter the parameters. I assume that "tool diameter" should be the shank diameter (3/16) rather than the cutting diameter (0.180). Does 3.2ipm at 3500 rpm (so that I don't have to move the belt) seem reasonable? I hate to break things!

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    Default Re: Thread milling questions

    Try this calculator

    Micro 100 Speed and Feed Calculator


    I entered .180 cutter diameter 4 flute, put in a max rpm of 5000. You want the cutter diameter to calculate your feed rate, not the shaft size.

    and its saying at 5000rpms, to run it at 25ipm. Delrin is very forgiving when it comes to thread milling, a great material to practice it on.

    Work: Hurco VMX42/VMX50 - Shopsabre 4896 - Bobcad V4 4axis pro
    Home: RF45 with Ajax CNC Controller - Bobcad V27 3 axis pro


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    Default Re: Thread milling questions

    Quote Originally Posted by kstrauss View Post
    I assume that "tool diameter" should be the shank diameter (3/16) rather than the cutting diameter (0.180).
    Absolutely NOT! Tool diameter is ALWAYS the outer diameter of the cutting teeth! For a threadmill, it is the OD of the profiled teeth. For threadmilling, you also want to compensate the feed for the helical path. This means feedrate will be much HIGHER when cutting external threads, and LOWER when cutting internal threads. I don't use GWizard, so can't give any specific advice for that tool. I VERY much prefer HSMAdvisor for all feed and speed calculations.

    Regards,
    Ray L.



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    Default Re: Thread milling questions

    I tried the Micro 100 calculator (thanks MikeC8!) which claims to be a version of HSMAdvisor.

    I understand that you need the tip diameter to calculate the feed rate (based on the diameter of the tool path) plus to get the SFM based on cutter RPM. I assume that you need the tool length and neck diameter plus DoC to ensure that you don't break things by feeding too aggressively. The Micro 100 calculator asks for tool length but not the neck diameter. Perhaps I'm missing it (what is "APT"?) but I don't see DoC.



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    Default Re: Thread milling questions

    Quote Originally Posted by kstrauss View Post
    I tried the Micro 100 calculator (thanks MikeC8!) which claims to be a version of HSMAdvisor.

    I understand that you need the tip diameter to calculate the feed rate (based on the diameter of the tool path) plus to get the SFM based on cutter RPM. I assume that you need the tool length and neck diameter plus DoC to ensure that you don't break things by feeding too aggressively. The Micro 100 calculator asks for tool length but not the neck diameter. Perhaps I'm missing it (what is "APT"?) but I don't see DoC.
    The F&S tools don't care about "neck diameter". It is your responsibility to ensure you don't try to cut threads that are too deep for the tool. In use, you'll be making cuts only a few thou or at most tens of thou, deep, not burying the tool anywhere near the point that neck diameter is any kind of issue.

    APT is Advance Per Tooth, basically chipload. DOC is something you get to pick, keeping in mind threadmills are rather fragile tools. Start light, and see what works. It will vary widely depending on the tool, and the thread size being cut. Usually when threadmilling, I will make multiple passes, keeping feed as high as possible, and allowing for a 0.005-0.010" final pass. It rarely takes more than 2, or at most 3, passes, and results in very smooth, close-fitting threads.

    Regards,
    Ray L.



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    Default Re: Thread milling questions

    Quote Originally Posted by kstrauss View Post
    I tried the Micro 100 calculator (thanks MikeC8!) which claims to be a version of HSMAdvisor.

    I understand that you need the tip diameter to calculate the feed rate (based on the diameter of the tool path) plus to get the SFM based on cutter RPM. I assume that you need the tool length and neck diameter plus DoC to ensure that you don't break things by feeding too aggressively. The Micro 100 calculator asks for tool length but not the neck diameter. Perhaps I'm missing it (what is "APT"?) but I don't see DoC.
    The calculator at Micro100 website is a clone on online FSWizard that I made available fir them.
    It is not HSMAdvisor.

    And unlike anything else, HSMAdvisor actually considers the neck diameter and length when making calculations.

    That said, you will not have any problems cutting delrin.
    Just make sure to pick parameters that your machine will handle.

    Tormach may not be able to accurately interpolate holes at high feed rate.

    http://zero-divide.net
    FSWizard:Advanced Feeds and Speeds Calculator


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    Default Re: Thread milling questions

    Thanks to everyone for their help. I used the PP conversational tab and successfully threaded some test pieces. I hate pressing Cycle Start with a delicate $35 tool!



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    Default Re: Thread milling questions

    Quote Originally Posted by zero_divide View Post
    ...Tormach may not be able to accurately interpolate holes at high feed rate.
    I regularly thread mill 4-40 holes in steel. The Tormach works well interpolating the small circles at around 5ipm, so I work backwards from that and the chip load to determine rpm.



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    Default

    Quote Originally Posted by kstrauss View Post
    Thanks to everyone for their help. I used the PP conversational tab and successfully threaded some test pieces. I hate pressing Cycle Start with a delicate $35 tool!
    $35.00 ? that's cheap for a threadmill -.



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    Default Re: Thread milling questions

    From Tormach.



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