ShopBot CNC Router Class
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Introduction: Cutting Tools

There are two basic kinds of cutting tools for the ShopBot: drill bits and end mills (or router bits).

Drill bits

  • These are the same bits used in a hand drill or drill press.
  • They are only for drilling holes, and only work when moving straight down.

End mills & router bits

  • These bits are designed to cut while moving sideways through the material.

There are two common styles of end mills, regular and ball end.

  • A regular end mill has a flat end, and is used for cutting at surfaces.
  • A ball end mill has a hemispherical end, and is used for 3D machining and finishing passes.

Cutting tools have two parts, the shank and flute.

The flutes are the cutting edges of the bit. The shank is the section that goes into the tool holder.

The shank must always be the same diameter as the tool holder. The flutes may (or may not) be the same diameter as the shank.

Some bits are available as up-cut, down-cut or compression spiral.

  • Up-cut
    • Sawdust is ejected from the top of the workpiece.
    • They damage the top layer of material.
    • They tend to lift the workpiece off the table. Be careful with workholding.
  • Down-cut
    • Sawdust is pushed into the workpiece.
    • They push the workpiece down onto the table.
  • Compression spiral
    • A combination bit (down-cut on top & up-cut on the bottom) designed to cut all the way through sheetgoods in a single pass.