Early on in planning the design for the Quadrotor, we knew that eventually some of the metal parts would need to be milled.  Having very little milling experience, other than a couple of basic-use classes at TechShop, I had no milling experience.  When it came time to start buying router bits for the ShopBot and Tormach CNC routers, I didn’t know what kind of bits were necessary.

Understanding End Mills

Greg over at 100kGarages put together a primer titled CNC Router Bits Demystified, which does a great job of explaining the basics of an End Mill, Ball Nose, Downcut, Upcut etc.


In his Article, Greg mentions some bits he recommends.  From my experience so far here are the 3 Carbide mills I bought, which are sold through Amazon (direct links):

  • 1/2″ End Mill 2-Flute.  – This is really good for hogging out massive amounts of material or quickly cutting profile (cut outs).
  • 1/4″ End Mill 2-Flute.  This is the workhorse bit I have been using for my projects, which have a relative amount of detail.
  • 1/8″ or 1/4″ Ball Nose End Mill 4-Flute.  – If you want a nice finished edge or smoother 3d milling features, a ball nose is necessary.  I have both a 1/8″ and 1/4″ ball nose, but have found it is pretty easy to snap a 1/8″ while its results aren’t significantly better than the 1/4″.

Also, for the smaller bits, you should probably go ahead and buy two.  You are going to break a bit.  When it happens, review your feeds and speeds then try again.


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