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  1. #1
    Join Date
    May 2013
    Toogoolawah, Queensland

    Question CNC Benchtop Mill Conversion - MT3 or R8


    I have decided to commence a project to build a CNC Benchtop Mill. I already have a Sieg manual mill that has an MT3 spindle, and I have a large amount of MT3 tooling.

    When I buy the manual mill that will be the basis for the CNC Conversion, should I buy one with an MT3 spindle so that I can use the existing tooling that I already own (my current first preference), or should I buy a Mill with an R8 spindle ?

    I've had some people advise me that an R8 spindle is far superior on a CNC Mill. Why - what makes R8 superior ?

    Are there some disadvantages to using an MT3 spindle on a CNC Mill?

    I hope some of the experienced people on this forum can advise.

    Many thanks,

    Manufacturer of the Finest Quality Swarf.

  2. #2
    Join Date
    Jul 2016


    A few things I can think of.

    Morse taper can be very hard to eject as it's a locking taper, no chance you would ever get an ATC to work I wouldn't think, also has no feature to ensure its inserted in the same orientation each time.

    In terms of rigidity I'm not sure, probably about the same, the wider throat of R8 might give it the edge. R8 collets are certainly massively better than mt3 in every way if you use them.

    I'm sure someone will chip in and say neither are very good, and they would be correct but in small machines you don't have much choice.

  3. #3
    Join Date
    Mar 2012


    The only advantage R8 has over Morse 3 is the ease of ejection, that been said i have seen but not used an Optima machine in morse 3 with a captive draw bar that ejects the tool ,i have not seen that on a R8 machine

    i think you have answered your own question, as you have the Morse 3 tooling buy a machine with a Morse 3 spindle

    both R8 and Morse 3 have limitations in repeatability of the Z height

    as far as Automatic tool change, neither is well suited, and in un altered form i don't think there is such a beast, and if you want to go to the Tormach TTS system (with its inherent limitations) Morse 3 and R8 can be used

    if you had the option of a BT30 spindle ,yes this is leaps and bounds ahead of both R8 and morse 3

  4. #4
    Join Date
    Sep 2009


    What you really want is BT30 / ISO30.

    R8 and MT3 are not designed for CNC and are problematic for implementing a toolchanger

  5. #5
    Join Date
    Nov 2019

    Default Customized CNC parts as per your requirements

    Quote Originally Posted by pippin88 View Post
    What you really want is BT30 / ISO30.

    R8 and MT3 are not designed for CNC and are problematic for implementing a toolchanger

    You can take help from the CNC machining specialist to manufacture a specialized product as per your requirements.

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