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IndustryArena Forum > Other Machines > Commercial Products / Manufacturers Support Forums > Charter Oak Automation Support Forum > Is the 12z good for CNC conversion? Concerned about low rpm tapping/high rpm milling
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  1. #1
    Join Date
    Jan 2014
    Posts
    11

    Is the 12z good for CNC conversion? Concerned about low rpm tapping/high rpm milling

    Im considering a 12z charter oak mill for a cnc conversion because of its larger table space, but Im concerned about the way Im seeing belt drives configured on these machines.

    I want to be able to tap lets say a 1/2-13 hole in aluminum at say 100rpm (just an example) and go straight back to milling at 5000rpm+ without changing pulleys.

    I understand that the high rpm will require a different motor. Is this possible? When you switch to a belt drive are you still using the geared head or is it eliminated?

    Thanks for any answers!

  2. #2
    Join Date
    May 2008
    Posts
    1185

    Re: Is the 12z good for CNC conversion? Concerned about low rpm tapping/high rpm mill

    The gear heads are not real great at 5000 RPM. I have run the IH mill for years and a 1/2 13 tap is easy. For high speed a belt drive and AC spindle bearings are best.

    I dont know how well people have done with the stock gears and spindle bearings at 5K. The stock speed is 1800 with a "standard" 1850 RPM motor. You can change to a 3600 RPM and a VFD and get 5K and I plan on doing that soon to a gear head PM-940m but I'm not planing on running 5K all day long but more like 3K.
    youtube videos of the G0704 under the name arizonavideo99

  3. #3
    Join Date
    Jan 2014
    Posts
    11

    Re: Is the 12z good for CNC conversion? Concerned about low rpm tapping/high rpm mill

    Thanks for the response,

    Is it practical to drive the spindle with a belt drive and eliminate the gears? Besides replacing the bearings and installing a belt drive is there anything else necessary or problematic in turning an IH mill to a high rpm machine?

  4. #4
    Join Date
    Jan 2014
    Posts
    11

    Re: Is the 12z good for CNC conversion? Concerned about low rpm tapping/high rpm mill

    Quote Originally Posted by arizonavideo View Post
    The gear heads are not real great at 5000 RPM. I have run the IH mill for years and a 1/2 13 tap is easy. For high speed a belt drive and AC spindle bearings are best.

    I dont know how well people have done with the stock gears and spindle bearings at 5K. The stock speed is 1800 with a "standard" 1850 RPM motor. You can change to a 3600 RPM and a VFD and get 5K and I plan on doing that soon to a gear head PM-940m but I'm not planing on running 5K all day long but more like 3K.
    I checked my email, and I believe you answered my question. Just eliminate the gearing, upgrade the spindle bearings, and install a belt drive to get the RPMs I want. Just to clarify I could potentially tap a hole around 100rpm and go back to milling around 5000rpm without changing pulleys?

  5. #5
    Join Date
    May 2008
    Posts
    1185

    Re: Is the 12z good for CNC conversion? Concerned about low rpm tapping/high rpm mill

    Well in steel with a 1/2" tap in high range with a 2HP motor it might be a problem.

    I did run a single speed belt drive at a .9 to 1 ratio and a 3hp 3600 RPM motor for year + and you could stall it with a larger tap.

    https://www.youtube.com/watch?v=4dmfP5i2syQ

    A few things could be done.

    A larger VFD will make more peak current. This one was only 2000 watt.

    A 1750 RPM motor makes twice the torque but at 5000 RPM it will make less power and more noise.

    Run a 5hp.

    You can over drive the motor at low RPM to get more torque but the duty cycle need to be short. A 15 second tap is fine, 40- 1/2" taps would not work well.

    Run the tap faster.

    I tap slow but really you can go much faster that I go. The motors make more power at higher speed.

    I still have the single speed drive and its extra.
    youtube videos of the G0704 under the name arizonavideo99

  6. #6
    Join Date
    Jan 2010
    Posts
    77

    Re: Is the 12z good for CNC conversion? Concerned about low rpm tapping/high rpm mill

    Arizonavideo makes a high quality belt conversion and I highly recommend it. Couple with a VFD you will have tremendous speed control.

  7. #7
    Join Date
    Apr 2016
    Posts
    17

    Re: Is the 12z good for CNC conversion? Concerned about low rpm tapping/high rpm mill

    Quote Originally Posted by saabman View Post
    Arizonavideo makes a high quality belt conversion and I highly recommend it. Couple with a VFD you will have tremendous speed control.
    I'm not certain he is making these any more?

  8. #8
    Join Date
    May 2008
    Posts
    1185

    Re: Is the 12z good for CNC conversion? Concerned about low rpm tapping/high rpm mill

    I'm not doing them right now mainly because I'm too busy making other things.
    youtube videos of the G0704 under the name arizonavideo99

  9. #9
    Join Date
    Mar 2006
    Posts
    1

    Re: Is the 12z good for CNC conversion? Concerned about low rpm tapping/high rpm mill

    Quote Originally Posted by JGanch View Post
    Im considering a 12z charter oak mill for a cnc conversion because of its larger table space, but Im concerned about the way Im seeing belt drives configured on these machines.

    I want to be able to tap lets say a 1/2-13 hole in aluminum at say 100rpm (just an example) and go straight back to milling at 5000rpm+ without changing pulleys.

    I understand that the high rpm will require a different motor. Is this possible? When you switch to a belt drive are you still using the geared head or is it eliminated?

    Thanks for any answers!
    The solution is the CNC conversion with the belt drive. Forget the tap and mill the threads with a thread mill. This is also a big advantage because if you break a tap it is hard to remove, the thread mill can be removed easily if you break it. I regularly mill 1/2"-13 , 5/8"-11 internal threads and 1"-32 external and internal threads threads for camera lens adapters with my IH-cnc (Charter Oak cnc). All of these are cut with the same single profile thread mill, one tool multiple threads.

  10. #10
    Join Date
    May 2008
    Posts
    1185

    Re: Is the 12z good for CNC conversion? Concerned about low rpm tapping/high rpm mill

    Just for fun here is some high speed milling with the IH mill.

    I need to do a correction to the feeds and speeds because I see that my Y axes was set to 60 IPM and the X was at 90.

    I'm going to re do the video with the settings set to 110 IPM for a better effect.

    https://www.youtube.com/watch?v=5fxhPBjVqXY
    youtube videos of the G0704 under the name arizonavideo99

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