4th Axis running as CNC lathe using milling machine

This is a discussion on 4th Axis running as CNC lathe using milling machine within the Milling Machine Builds & Conversions forums.

  1. #1
    Jonathan's Avatar
    Lives in Leicester (Home) or Nottingham University (2nd Home), United Kingdom. Current Activity: Viewing Forum Superstar, has done so much to help others, they deserve a medal. Has been a member for 3-4 years. Has a total post count of 3,215. Received thanks 258 times, giving thanks to others 8 times.
    My 500th post on this forum :surprised: ... something a bit different.

    A few months ago I started making a 4th axis for my milling machine, or router. My reason for doing this is to have it belt driven, thus faster than the vertex rotary table I converted and capable of being used as a lathe. This is the original design:

    4th Axis running as CNC lathe using milling machine-4thaxis7.jpg

    4th Axis running as CNC lathe using milling machine-4thaxis11.jpg

    4th Axis running as CNC lathe using milling machine-4thaxis12.jpg

    It includes solenoids to make a disk brake which should mean I can get a much higher holding torque than with the stepper motor alone when stationary.
    I machined the shaft and bearing housing at school since they were much to big for my mini lathe, and CNC milled all the slots for the solenoids using the rotary table. The hole through the spindle is 1". I press fitted the tapered roller bearing outer rings.

    4th Axis running as CNC lathe using milling machine-dsc06175_small.jpg

    4th Axis running as CNC lathe using milling machine-dsc04465_small.jpg

    Recently I got round to making and fitting the timing pulley so I thought it was time for a test. I've not made the mount for any motor yet, so I just used the large brushless motor I'd converted to a spindle, put a pulley in its chuck, and stuck it in a vice. Crude, but it works for now. Shown below is it set up to machine the front of the spindle, the same as my C3 lathe, to fit the chucks I have. I left this bit until last since machining this in place should minimise the runout:

    4th Axis running as CNC lathe using milling machine-dsc07171-medium-.jpg

    4th Axis running as CNC lathe using milling machine-dsc07174-medium-.jpg

    Spindle after machining:
    4th Axis running as CNC lathe using milling machine-dsc07172-medium-.jpg

    The motor, though only run on 24V from some big batteries - not the 48V that it is rated for, and geared for 2900rpm works well at the much lower rpm required to machine the face of the spindle which is 80mm diameter.

    At the moment my method for mounting the lathe tool is distinctly dodgy. Not surprisingly it vibrated a fair bit. At some point I shall make a proper tool-post that bolts onto the milling machine somewhere else, not to the quill.

    Just as a test I tried machining a 22mm diameter hemisphere onto a piece of aluminium bar, and a similar size hemisphere on to the end of a 20mm diameter mild steel bar. I will upload the videos shortly, here's some pictures of the result. Not great, but it's hardly surprising with the way the tool was mounted and the tool I used:

    4th Axis running as CNC lathe using milling machine-dsc07193-medium-.jpg

    4th Axis running as CNC lathe using milling machine-dsc07189-medium-.jpg

    4th Axis running as CNC lathe using milling machine-dsc07188-medium-.jpg

    The next stage for this is to make the motor mount incorporating brushless and stepper motor and probably a dual timing belt reduction to get around 10:1 ratio for the stepper motor. Then I will add the solenoids, if necessary.

  2. #2
    Jonathan's Avatar
    Lives in Leicester (Home) or Nottingham University (2nd Home), United Kingdom. Current Activity: Viewing Forum Superstar, has done so much to help others, they deserve a medal. Has been a member for 3-4 years. Has a total post count of 3,215. Received thanks 258 times, giving thanks to others 8 times.
    Here's the video:

    Last edited by Lee Roberts; 03-04-2012 at 08:03 PM. Reason: added vid

  3. #3
    blackburn mark's Avatar
    Lives in blackburn, United Kingdom. Last Activity: 01-02-2014 Has been a member for 3-4 years. Has a total post count of 586. Received thanks 30 times, giving thanks to others 17 times.
    splendid !! i like it, iv opted for the harmonic drive so there'll be no turning on mine but im well chuffed with how well it works... i should get a vid up to show it off :)

    where the hell do you find time to go to uni ???? youll fail all your exams but be a top notch engineer :)

  4. #4
    Jonathan's Avatar
    Lives in Leicester (Home) or Nottingham University (2nd Home), United Kingdom. Current Activity: Viewing Forum Superstar, has done so much to help others, they deserve a medal. Has been a member for 3-4 years. Has a total post count of 3,215. Received thanks 258 times, giving thanks to others 8 times.
    Just realised I've forgotten to reply to this

    Quote Originally Posted by blackburn mark View Post
    splendid !! i like it, iv opted for the harmonic drive so there'll be no turning on mine but im well chuffed with how well it works... i should get a vid up to show it off :)
    Where did you get the harmonic drive / which one? Please do put photos up! A harmonic drive looks like a great way to do a B/C axis to rotate the spindle - something I would like to do on my router once I've made the sturdier frame.

    Quote Originally Posted by blackburn mark View Post
    where the hell do you find time to go to uni ???? youll fail all your exams but be a top notch engineer :)
    :heehee::heehee:

  5. #5
    blackburn mark's Avatar
    Lives in blackburn, United Kingdom. Last Activity: 01-02-2014 Has been a member for 3-4 years. Has a total post count of 586. Received thanks 30 times, giving thanks to others 17 times.
    howdy jonathan, i stalked ebay for months to get this harmonic drive... think i paid about 110 for it, it was in mint condition...i think it was pulled from a prototype that didnt quite come to anything and was a costom order from LLC 60:1 ratio (strange)

    iv just rendered out a video with it in, ill try to post it up on the forum in a mo, itll give you an idea of what i did :)

  6. #6
    luke11cnc's Avatar
    Lives in Rugby, UK, United Kingdom. Last Activity: 11-07-2013 Has been a member for 2-3 years. Has a total post count of 376. Received thanks 9 times, giving thanks to others 26 times.
    hay Jonathan that's pretty good mate.

  7. #7
    Jonathan's Avatar
    Lives in Leicester (Home) or Nottingham University (2nd Home), United Kingdom. Current Activity: Viewing Forum Superstar, has done so much to help others, they deserve a medal. Has been a member for 3-4 years. Has a total post count of 3,215. Received thanks 258 times, giving thanks to others 8 times.
    Yes ... it works. It would be much better if I made a proper toolpost. At the moment the setup is very limited due to the clearances round the spindle.

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