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Understanding the variables involved milling with the MiniMill

Discussion in 'CNC Mills/Routers' started by David Paxson, Dec 29, 2017.

  1. David Paxson


    Oct 4, 2017
    Likes Received:

    I completed the build of our MiniMill about a week ago. I've been trying to wrap my head around what things can vary and how should I adjust them.

    So things that can vary include:
    1. The type of material being cut (soft wood, hard wood, MDF, plastics of various sorts, aluminum, other metals)
    2. The speed of the spindle
    3. The size of the end-mill
    4. The type of the end-mill
    5. The feed rate
    I just don't understand what speed I should be running the spindle at, what feed rate to use, what are the best end-mills to use or sizes.

    Any guidance would be appreciated. I am most interested in milling aluminum and plastics (specifically acetal).


  2. GrayUK

    GrayUK Openbuilds Team Elder
    Staff Member Moderator Builder

    May 5, 2014
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  3. Joe Santarsiero

    Joe Santarsiero OB addict
    Staff Member Moderator Builder

    Oct 30, 2014
    Likes Received:
    A lot of tool manufactures also provide some info on feeds and speeds to put you in a ballpark. The material also will have a recommended cutting speed that you can Google. Take these figures and enter them into a feed speed calculator and you should get a few other numbers out.
    I use fusion360 and it has a built in calculator. I usually give it a feed per tooth with a cutting speed and see what it auto fills for Rpms and then tweak things a little. Try the cut and fine tune from there. Then, I'll document the tool, material, lube, and cutting info for future reference updating it on occasion.
    I don't care to recommend tooling with feeds and speeds on these diy machines because they all have their own variables that can affect the outcome. What might work well on my machine might turn horrid on someone else's. Of course it is a nice thing when someone has an identical setup.
  4. Kevon Ritter

    Kevon Ritter Veteran

    Apr 30, 2015
    Likes Received:
    In order to determine what a good starting point would be, you have to understand what's actually going on at the cutting edge. If you just plug in a number and expect it to work, things are probably going to go wrong very fast, and you still will have no clue why. A good starting point would be cnccookbook. I haven't looked at it all, but stuff that I did particularly seek seemed accurate and straightforward.

    They have a full guide. Don't ask for it. Understand it, then apply it.
    CNC Feeds and Speeds: Cutting Speeds for Every Situation

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