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  1. #13
    Join Date
    Jan 2007

    Re: How well do the belt drive conversions work when milling steel?

    Oh, I have the pulleys made already. Actually, they've been done for a couple of years. They are 10 groove micro belt pulleys. One is mounted to a splined hub that will drive the splined spindle and the other fits on the motor shaft. And the splined hub is made as well. Where I stalled out was on the tool holders. Drifting from R8 to TTS to CatR8 in my thinking and finally to BT30. That was a two year drift trying to make the case and do some minor testing for each type and I put everything else on hold until I got the spindle solved. And of course it has taken some time to gather the tool holders for the new spindle, but I'm back going on the belt drive conversion as soon as the chip enclosure is finished.

    After testing the new motor, my confidence is pretty high on it being able to deliver if I don't get stupid in my programming. It did take me some experimenting in Mach to figure out the use of the pulleys to get my rpm ranges right, but now that I got that the motor seems to run in ranges that keeps the rpm in full torque mode. So the only doubt I have any more is on belt slippage. My use of the micro v belts this past year on the two other machines I have has shown them to be real dependable in that regard. Even in completely stalling the 1 1/2 hp motor on one of those machines, the belt never slipped a bit. So I'm getting some confidence in them to deliver on the mill. Trying to stall the new 3 hp motor on the test stand even at 300 rpm hasn't worked, so I'm getting some confidence there as well. But like everything else, it's all theory until I put it in use. Hope that's soon.


  2. #14
    Join Date
    Oct 2008

    Re: How well do the belt drive conversions work when milling steel?

    "And I want to get to thread milling at some point."

    Thread milling is nice in that its pretty forgiving of precision in spindle speeds. I've single point threaded (5 flute) 1018, 303 stainless, 304 stainless, and a variety of aluminum and plastics with good results. Its obviously nowhere near as fast as rigid tapping, but IMO if you have the CAM for it then its much easier. Just take a few passes and a spring pass or three. Multi point thread milling is obviously faster, but you will need a few more thread mills for different thread pitches.

    Thread mills do tend to be a bit expensive, but they are worth it if you need them. One guy I know grinds off two out of three flutes on hand taps, and then back grinds the third for his own style of thread mill. Probably works ok for through holes and modest tolerance threading. I don't recall all the details.
    Bob La Londe

  3. #15
    Junior Member
    Join Date
    Sep 2017
    Any chance you still have pulley kits? Or are you done? I’ve made pulleys for other equipment though time is crunched lately so a known working set would be great.

    Quote Originally Posted by arizonavideo View Post
    " My concern of less torque from a belt drive vs the geared head"

    You have said a few times about the torque loss of a belt drive. I know you don't have quite the reduction that you get with the gears but the reduction in low range is about 2.3 to 1.

    With a 3 hp motor you will never stall the mill if the VFD is set up properly with its RPM compensation set to a good level.

    I do have a extra 10 groove pulley that I could let go for cheep. I have changed the offset that I used to allow for the last grove to be thicker so this one is a bit thin.

    It is the motor pulley for a 1750 motor and is cut to accept a QC bushing. You do need a long shaft motor. For the short shaft IH motors I make the motor pulleys taller.

    I'm to busy right now to do any more belt drives but I mostly do all 8 groove pulleys anymore so I don't need this one.


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