Carving Bits 101 - Bit Basics




To be a successful 3D carver, it's important to understand which bits to use with which materials in order to achieve optimal results. There are a ton of things to know about different materials and different bits. Whether you're new to 3D carving or an advanced user, it can feel overwhelming when you're trying to figure out what bit to use for your specific project. 

This guide is designed to help you understand milling bits. The more you know about bit characteristics, the better prepared you will be for deciding which bit to use with which materials. Our Easel Live episode, above, goes into more depth if you want to learn more.

Use these links to jump to a specific part in this article: 

Milling Bits vs. Drilling Bits 

What's the difference?

Bit Material

High-speed Steel, Solid Carbide, and Carbide-Tipped

Number of Flutes

1 flute, 2 flute, or 2+ flutes

Flute Type

Upcut, downcut, straight cut, and compression

Bit End

Fishtail, ball nose, v-bit, and engraving

Bit and Material Example Photos

 



Milling Bits vs. Drilling bits

If you're new to 3D carving, you may be curious why we use milling bits (also called end mills, cutters, or carving bits) instead of drill bits. While it may be tempting to use the drill bits you likely already own, it's important that you use milling bits for your 3D carving projects: there's a very distinct difference in the way these different types of bits work.

Source: Make: Magazine
  • Drill bits cut down into your material. They are a great choice pre-drilling holes for screws, adding fixtures to drywall, or other tasks where you need to remove material straight down through an object. 
  • Milling bits cut laterally across your material. The bits are designed to move across the surface of a material, clearing away chips as it moves from side to side. This is how you are able to achieve 2.5D and 3D designs with a 3D carving machine instead of a drill or drill press.

Bit Material

Steel (High-Speed Steel body, or HSS)

  • Primarily used for hand-routing, but also good for 3d carving
  • Tough body.
  • Sharper cutting edge than carbide. As such, they are often used for milling aluminum.
  • Good for beginners!
    • Cheaper than carbide bits
    • More forgiving when carving (less likely to break)
  • These bits often have a narrower cutting speed range than carbide bits. It's important to know the recommended feeds/speeds for a specific bit. You can often find this information from the bit manufacturer.
  • Steel bits tend to be specialized for certain tasks. We don't recommend them for generic projects across a lot of different materials. 

Solid Carbide

  • Most bits (including many on our site) are solid carbide. 
  • Most rigid. This is important for minimizing bit deflection and keeping straight toolpaths during a carve.
  • Long tool life. You'll get what you pay for with these bits!
  • More expensive, especially compared to HSS bits.

Carbide-tipped

  • Hybrid bit: body is made from HSS, but the tip is carbide. This gives you the best of both worlds:
    • Toughness of steel bit body
    • Wear-resistance of carbide flutes
  • Good price-point for beginners and advanced carvers alike.
    • Beginners: not too expensive if you're just getting started and breaking a few bits. You'll be able to do a wider variety of projects with a few carbide-tipped bits instead of buying a lot of bits for specific tasks.
    • Advanced: If you're carving a lot, these bits are good utility players. You can use them for a lot of different projects without buying solid carbide bits.

Number of Flutes

Flutes are the cutting edges on the bits. They have different shapes, and bits have different numbers of flutes. The number of flutes on a bit determines the chip load (how quickly chips are removed from your material). 

1-2 flutes:

  • More material is ejected with each rotation. Chips are larger because the bit is removing more material each time the bit rotates.
  • Faster, rougher cuts. These are great for prototyping, 
  • More room to eject the chip. Chips are dispersed farther away from the cutting surface. 
  • Recommended for: 
    • Soft plastics
    • HDPE
    • Acrylic
      • Use 1 flute bits on plastics like HDPE and acrylic.
        • Clear chips away from the bit as quickly as possible. This prevents chips from sticking back to the material, your bit, or ruining the carve. 
        • The more flutes you use, the more heat that is generated by the bit. More heat means chips are more likely to reweld or gunk up the bit. Using fewer flutes helps minimize the number 
    • Aluminum

2+ flutes:

  • Less material ejected with each rotation
  • Smoother surface finish. These bits are great for detailed work or "finishing passes" (using a second bit to clean up the toolpath generated by a roughing bit during a 2-stage carve.)
  • Slower cuts
  • Less room to eject the chip
  • Recommended for:
    • Corian
    • Hardwoods
    • Hard materials

 


Flute Type

Flute type determines the direction the chips are dispersed—up, down, or out—when the bit removes chips from the stock material. Chip dispersal is important for different material types. 

Upcut

  • Ejects chips up and away from your bit and the stock materials. This minimizes chip rewelding for materials prone to melting (like acrylic and HDPE).
  • Use upcut bits for a clean finish on the bottom surface of your material when cutting all the way through your material.
  • For all toolpaths, this bit generates rough edges on the top surface of your material. There will likely to be a lot of fringe at the top of your material, on top surface, also known as tearout.
 
  • Recommended for:
    • Plastics (acrylic, HDPE)
    • Aluminum
    • Expanded PVC
    • Any material where heat buildup is a concern
  • NOT recommended for: 
    • Plywood

Downcut

  • Pushes chips back down into the stock material. 
  • For all toolpaths, these bits leave a clean surface on the top side of your material. They leave a rough finish on the bottom surface of the material on thru-cuts.
  • The downward motion of the flutes helps hold material down against the waste board. As such, downcut bits are great for thin pieces of materials (1/8" depth or thinner). 
  • Due to its surface finishing, these are our favorite bits for creating pockets (for an inlay) or any cut that doesn't go all the way through your material.
 
  • Recommended for:
    • Plywoods
    • Laminates
  • NOT recommended for: 
    • Acrylic
    • HDPE
    • Aluminum

Straight Flute:

  • Chips are dispersed out from the stock material: not up and not down. These bits don't pull up on your material or push your material downwards. 
  • Excellent for minimizing chipping and fraying on the top surface of the material.
  • These are good to keep in your arsenal as general purpose bits.
 
  • Recommended for:
    • Bamboo
    • Plywoods
    • Any material where splintering and fraying is an issue
  • NOT Recommended for: 
    • Acrylic
    • Expanded PVC

Compression

  • The flutes spiral in both directions: up and down.
    • Upcut flutes on the bottom of each flute. This pulls chips away from the stock material as the bit generates new toolpaths.
    • Downcut flutes on top of each flute. This acts as a finishing path to leave a smooth surface on the top of the stock material surface, removing any tear out or fringe generated by the upcut flutes. 
  • These are the best bits for laminated materials or thru-cuts, because these bits leaves a good finish on the top and bottom of the material.


Bit End

The end of the bit impacts what the bottom of the toolpath looks like. This is important to consider for things like pockets or engravings. 

Fishtail

  • Bit end has flutes that produce a flat surface with a clean edge.
  • Fishtails are good for plunge cutting. This also makes them an excellent choice for thinner materials, because they are less likely to splinter or damage thinner materials.
  • Use this bit to make pockets with flat bottoms.
  • Versatile for a lot of different material types, but especially plastics.

Ball Nose

  • Bit end is rounded, which produces a path with curved edges.
  • If you’re cutting layers in several steps, ball nose bits reduce the risk of creating jagged steps. This makes them great for sculpting and 3D modeling (i.e. domes, complex surface curves, etc.)
  • This bit type can leave “rippled” grooves in pockets if your stepover is too high (e.g. if your toolpaths don’t overlap enough).

V-Bit

  • These unique bits have a V-shape on the end for carving grooves into your material. 
    • Examples of v-carved toolpaths include tapered edges, varying widths and depths in the same toolpath, and beveled edges
  • Typically used for sign-making.
  • Use bits with different angles for different levels of detail.
    • The lower the degree, the more detail you can get (i.e. a 60-degree bit will give you more detail than a 90-degree bit).
  • V-bits are great for hardwoods. Only use a v-bit on plywood if you are running a test job, as the v-bit can cause severe tear out and splintering.


Engraving

  • Engraving bits are essentially v-bits with a very, very low degree. On our site, you'll find engraving bits as low as 30 degrees.
  • These bits are incredibly fragile. Don’t use for anything other than engraving. 
    • Don’t use an engraving bit for carving through material.
  • You can carve precise details on softer carving materials, like wood.
  • Not recommended for acrylic: bit is fragile and acrylic is hard
 

Bit and Material Example Photos











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