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Thread: Power feed for mini lathe and mini mill

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    dgbreggin's Tools

    Power feed for mini lathe and mini mill

    Some time ago, I added X-Axis power feed to my mini mill. (I'll post about this at a future time.)

    Shortly after, I decided that I should have power feed for the Y-Axis, as well as power feed for most operations on my mini lathe. I recently added a crank handle to the Z-Axis fine feed knob of my mini mill (posted here recently). I decided that this, too, should have power feed capability.

    The benefits of power feed include:
    * consistent speed, producing better finish
    * reduces operator fatigue during repetitive operations

    Requirements:
    * use without modifying machines
    * wide range of operating speed
    * low voltage (for safety)
    * easy reverse
    * easy "100% speed" for rapid traverse or tool withdrawal

    I decided to use 12V DC for this system. I purchased a PWM motor speed control with display, and a common 12V power supply as used for computers and similar electronic. Both sourced from Amazon.

    Since DC motors lose a lot of torque at reduced speed, I built 4 easily interchanged power drive units with different gearing. That way I could get a wide range of speeds without trying to operate the motors at low speed. All the motors turn at about 5k max RPM and have attached gear reduction for the rated RPM. After experimentation, I settled on 220, 120, 50, and 20 RPM. These motors, along with the mounting brackets, were sourced from Amazon.

    Power feed for mini lathe and mini mill-20220606_121408.jpg Power feed for mini lathe and mini mill-20220606_121427.jpg

    I used residential solar-panel type connectors and plugs (Amazon).

    The control box has an on-off switch, a speed display (%, not RPM), a speed control knob, and a "max speed" override switch. It also has the power connector, and 3 power drive unit plug-ins. I wanted to be able to use one power drive unit for slow cutting and another for fast withdrawal. Having multiple plug-ins allowed quick switching of the power drive units.

    Power feed for mini lathe and mini mill-20220605_154335.jpg

    The control box hangs on the front of the top drawer of either of the tool chests that have my machines on top. That way it doesn't clutter the workspace and can be removed and stored when not in use.

    Each power drive unit consists of a motor, a handle, and a control switch (forward, off, reverse). The motor shaft has a 2-1/4" extension with a 3/8" square drive that fits commonly available sockets. I installed a rubber O-ring at the end of the square to help retain the socket. The shaft extension allows the drive to be used without the various machine crank handles hitting the operator's fingers. The switches are common automotive power window switches. Press one side for forward and the other for reverse. Release the switch to stop.

    Power feed for mini lathe and mini mill-20220606_121320.jpg Power feed for mini lathe and mini mill-20220606_121343.jpg

    The power drive unit handle is 1" square aluminum tube. At the end is a round disk with the motor / gearbox mounted to it. It was designed so that I could pivot the handle to different positions, like "right hand" and "left hand". In practice I never use this feature so I would not go to that effort if I were going to build it again.

    Power feed for mini lathe and mini mill-20220606_121625.jpg

    I designed a "driver stem" with a hex that fits the socket on the drive unit (14mm in this case, though the size is not critical). It also has a flange that can easily be mounted to whatever type of drive adapter I might need to operate the various machine controls. This was made from 1" aluminum hex stock.

    Power feed for mini lathe and mini mill-20190825_113608.jpg

    I made the following adapters:
    * Mini-mill Y-Axis (also fits X-axis, FWIW)
    * Mini mill fine downfeed crank (crank project posted recently)
    * Rotary table
    * Mini-lathe cross-slide
    * Mini-lathe compound
    * Mini-lathe tailstock quill

    Power feed for mini lathe and mini mill-20220606_120740.jpg Power feed for mini lathe and mini mill-20220606_120833.jpg

    The adapters are designed to fit the crank / handle of the specific machine function. Most of the adapters will snap in place or are held in place by friction (supplemented with painter's tape, as needed). This makes it easy to remove the power drive unit between operations and/or swap power drive units.

    Power feed for mini lathe and mini mill-20190825_131322.jpg Power feed for mini lathe and mini mill-20190825_131410.jpg

    Power feed for mini lathe and mini mill-20220605_154003.jpg Power feed for mini lathe and mini mill-20220605_154025.jpg Name:  Downfeed.gif
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    Power feed for mini lathe and mini mill-20220606_121250.jpg

    What I might do differently:

    * As mentioned, changing the angle of the motor on the handle just isn't necessary with my setup.

    * I was not able to figure out how to get the display to show 100% when I used the max-speed override switch. If I were doing it again, I would probably add an indicator lamp to show when this switch is activated.

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  2. The Following 10 Users Say Thank You to dgbreggin For This Useful Post:

    bruce.desertrat (Jun 6, 2022), cjfearn (Jun 6, 2022), emu roo (Jun 6, 2022), Home-PC (Jun 6, 2022), Inner (Jun 6, 2022), joew49 (Jun 6, 2022), Jon (Jun 6, 2022), nova_robotics (Jun 16, 2022), rayh__ (Jun 6, 2022), uv8452 (Jun 11, 2022)

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    Thanks dgbreggin! We've added your Mini Mill Power Feeds to our Milling category,
    as well as to your builder page: dgbreggin's Homemade Tools. Your receipt:




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    Congratulations dgbreggin - your Mini Mill Power Feeds are the Homemade Tool of the Week!

    These are well thought-out power feeds, and the various adapters greatly extend their utility.

    Some more good builds from this week:

    Dot Peen Marking Method by rgsparber
    Brake by orioncons36
    Mill Spindle Modification by GBWM
    Lathe Lever Switch Modification by Frank S
    Mini Lathe Tool Rest by Guy Marsden
    Carver's Mallet by Philip Davies
    Fly Cutter by Rustinox
    Locking Knob Template by Didpoolhall
    Chisel and Turning Tool Rack by Mazay
    Rivnut Tool by Improvised DIY
    Pipe Welding Positioner by Topper Machine
    Automated Dust Collection Gate by thecuzdoes
    Chain Link Tool by Metalgeria

    dgbreggin - you'll be receiving a $25 online gift card, in your choice of Amazon, PayPal, or bitcoin. Please PM me your current email address and gift card choice and I'll get it sent over right away.

    This is your 2nd Homemade Tool of the Week. Here are both of your Homemade Tool of the Week winning tools. Congrats again



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    Don42's Tools
    Really nice project! One comment for future reference: Permanent magnet and shunt-wound DC motors do not lose torque at reduced speed. Torque is limited only by max current. As speed is varied by supply voltage or by a PWM controller, torque can be up to max from rated speed clear down to stall. Series wound DC motors as are commonly found in corded power tools deliver more torque at lower speeds.

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    old_toolmaker (Jun 11, 2022)

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    dgbreggin's Tools
    Quote Originally Posted by Don42 View Post
    Really nice project! One comment for future reference: Permanent magnet and shunt-wound DC motors do not lose torque at reduced speed. Torque is limited only by max current. As speed is varied by supply voltage or by a PWM controller, torque can be up to max from rated speed clear down to stall. Series wound DC motors as are commonly found in corded power tools deliver more torque at lower speeds.
    Great info. Thanks.

    Can you suggest specific motors like these that would work in this application?

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    Don42's Tools
    Your 20 RPM gear motor is rated at 0.31 kg-cm torque, at 0.6 amps. This 220 RPM 12-volt motor,
    https://tinyurl.com/2p8r37x7
    is rated for 0.875 kgf-cm of torque at 1.4 amps, or 2.8X the torque of your 20 RPM motor, so it could handle your entire range of speeds and loads. If driven by a little over 1 volt it would turn at about 20 RPM. The motors with greater gear reduction might be a bit "stiffer" (more constant speed) with varying loads, but a motor controller with speed feedback would be very stiff.

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    dgbreggin (Jun 11, 2022)

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    dgbreggin's Tools
    There has been a lot of interest, so I thought I'd post a couple more pictures.

    Power feed for mini lathe and mini mill-20220611_145854.jpg Power feed for mini lathe and mini mill-20220611_145923.jpg

    These are for the cross-slide. I made a similar adapter for the compound which is very handy for turning cones and tapers.

  11. The Following 2 Users Say Thank You to dgbreggin For This Useful Post:

    Jon (Jun 11, 2022), old_toolmaker (Jun 11, 2022)

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    old_toolmaker's Tools

    DC motors and controllers.

    Thanks for the great explanation of DC motor torque as it relates to permanent magnet motors. I recently replaced my Unimat series wound AC motors with 24v DC permanent motors and motor control. I now have great speed control with steady torque.
    Dick


    Links to some of my plans:

    https://www.homemadetools.net/forum/...965#post105972 OFF-SET TAILSTOCK CENTER PLANS
    http://www.homemadetools.net/forum/s...995#post112113 SMALL TURRET TOOL POST PLANS
    http://www.homemadetools.net/forum/l...994#post112111 LARGE TURRET TOOL POST PLANS
    http://www.homemadetools.net/forum/m...383#post110340 MINI-LATHE CARRIAGE LOCK PLANS
    http://www.homemadetools.net/forum/s...191#post106483 SMALL QC TOOL POST PLANS
    http://www.homemadetools.net/forum/q...849#post119345 QUICK CHANGE LATHE TURRET
    http://www.homemadetools.net/forum/m...949#post119893 MINI LATHE COMPOUND PIVOT MODIFICATION

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    dgbreggin's Tools
    UPDATE

    I purchased one of the motors recommended and built a handle for it.

    The new motor / handle weighs about 50% more than my earlier ones. This is the only down side, and it is quite minor.

    The power available at lower speed is much better than the previous motors. I may still use one of my existing low speed motors when I need really slow movement, which is rare, but for everything else I can now use a single unit.

    This is a big improvement. My thanks to Don42 for his insight and assistance.

    Here are some pictures.

    Power feed for mini lathe and mini mill-20220613_133409.jpg Power feed for mini lathe and mini mill-20220617_104741.jpg

    Power feed for mini lathe and mini mill-20220617_104749.jpg Power feed for mini lathe and mini mill-20220617_104806.jpg

    There is a motor mounting bracket available, but it did not suit my installation very well so I just made my own. As I suggested in my first post, I did not make the handle angle adjustable this time.



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