CNC Router Essentials. Randy Johnson

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      CNC Router Essentials

       Toolpath Essentials : 3

      Additional useful bits

      V-bits are most commonly used for V-carving text and other fine details, Image 3.2. The smaller the angle of the V-bit, the finer the details it will be able to cut.

      Ballnose and core box bits are available in a variety of diameters and lengths, Image 3.3. Tapered ballnose bits are used for finishing intricate 3-D carvings. Like V-bits, smaller bits will create more intricate details.

      A spoilboard or fly cuer bit is helpful, but not imperative when starting out, Image 3.4. This type of bit is used to level the spoilboard on your machine. With its large diameter, it can cover a big area quickly. You can also surface your spoilboard with something more common, such as a " straight bit. It just takes longer.

      Which bits you’ll need for your work depends largely on the types of projects you plan to make, but here is a short list of bits that will get you started, and you can add to it as your needs expand.

      Image 3.4: A large diameter spoilboard bit is used to surface the MDF table when it becomes rough.

      Image 3.2: V-bits are available in different diameters and angles. They are mostly used for V-carving.

      Image 3.3: Ballnose and core box bits are available in a variety of diameters and lengths. Smaller diameters are tapered to increase strength and reduce breakage. Spiral ballnose bits are commonly used to machine intricate 3-D carving designs. For shallow low-detail carvings, a core box bit works well. Both bits can be used to create fluted designs.

      As you do more with your machine you may want to add: • 30° V-bit (fine V-carving and details)

      • "- and "-diameter ballnose bits (3-D carving)

      • "-diameter downcut spiral straight bit (general cutting)

      • "-diameter straight bit (fine profile and pocket cuts)

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      3 : Toolpath Essentials

      Frequently used toolpaths

      A CNC machine can make many types of cuts, but the four most commonly used are the Profile, Pocket, V-Carve, and 3-D Roughing and Finishing Toolpaths, Image 3.5. With an understanding and mastery of these cuts, you’ll be able to complete a variety of projects.

      Pocket cuts are used to create a recessed area in your workpiece, Image 3.6. The recess might simply be a design detail in your project, or it can be sized to accept another piece of material, such as buerfly inlay. A pocket cut can be square, rectangular, oval, or nearly any shape you can imagine.

      V-carving is used to create text that simulates incised handcarved leering, Image 3.7. But it works equally well on any “closed” line shape, such as the outline of an animal. By contrast, a single line with ends that don’t connect is considered an “open” line shape and cannot be V-carved. V-Carve is a very popular toolpath with CNC users and is a very simple way to add decorative carving to your project.

      3-D carving toolpaths include both roughing and finishing passes. They are used to carve 3-D models. The roughing pass is used to quickly remove the excess material and usually done with a straight bit, Image 3.8. The finishing pass is almost always done with a ballnose bit to create the fine details, Image 3.9. The diameters of the roughing and finishing bits depend on the size and detail of your project.

      Image 3.5: A CNC can make many types of cuts, but these four are the most commonly used ones. In the world of CNC, these cuts are also referred to as toolpaths.

      Image 3.6: The Pocket Toolpath typically uses a straight bit of some type to cut the recessed area.

      Pocket cut

      Profile cut

      3-D carving

      V-carving

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      CNC Router Essentials

       Toolpath Essentials : 3

      Profile cuts can be used to cut partly or completely through your work, Image 3.10. Think of it as a saw blade or dado blade that makes a cut partially or completely through the material. It is commonly used to separate the part from the surrounding material or to create grooves and slots.

      With these four types of CNC cuts, you can create a variety unique projects. Yet, we've only scratched the surface of what can be done with these cuts, as there are many other ways they can be used to enhance your CNC projects.

      Cutting direction

      Climb cuing with a handheld router or router table (moving in the same direction the router bit is spinning) can be dangerous since the bit can grab the material and

      Image 3.7: The V-Carve/Engraving Toolpath uses a V-bit to create decorative incised carving. It works equally well on text and non-text line designs.

      Image 3.9: A spiral ballnose bit is used to complete the finishing pass on a 3-D carving. Small-diameter ballnose bits taper up to the diameter of the shank to provide added strength to the cutting flutes.

      Image 3.8: Most 3-D carvings are cut in two steps. The first step is the roughing toolpath, which is often done with a straight or spiral bit to quickly remove the majority of the material.

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      3 : Toolpath Essentials

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