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Jan 2022

A Beginner’s Guide to Choosing CNC Router Bits

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A CNC router is a computer-controlled cutting machine that is used to cut and engrave various materials, including wood, composites, aluminium, steel, plastics, glass, etc with speed and precision. The term CNC stands for Computerized Numerical Control machines.

Even though 3 Axis routers are the most widely used CNC machines, 5 axis and 7 axis modes are also popular as they are also extremely capable and suitable for many applications. While CNC machines have opened all kinds of creative possibilities, the real magic lies in CNC router bits. CNC routers precisely determine the toolpath, and they require bits to make intricate cuts.


In this article, we explain different types of CNC router bits, their characteristics, and some important aspects while choosing the right CNC router bits for your projects.

CNC Router Bits & Their Uses

CNC router bits are the most essential as well as sensitive components of CNC Routers while performing cutting, engraving, pocketing or any other processes on workpieces. Bits govern the type of processing to perform on CNC routers and the quality of final designs. There are many distinct types of CNC router bits are available in the market, and each procedure requires the use of a specific bit.

In simple terms, CNC router bits can make the difference between cutting down on waste or drastically increasing material costs. Without the right bits, even the perfect CNC rig won't be able to give the best result.

The range of materials and designs cut by router bits has grown in diversity, and so have the types of CNC router bits. Today, the market is flooded with a broad spectrum of CNC router bits, making it a bit confusing to pick the right bit for a project.


Common Types of Bits

Based on the processing method, the CNC router bits fall into two major categories, i.e. CNC Drill Bits and CNC Milling Bits.

CNC drill bits are usually used for pre-drilling holes for screws as they drive into materials. They don’t have side edges, so they can’t mill horizontally.

CNC milling bits, also known as CNC carving bits, can cut or move across the surface of the workpieces. They are designed to carve or engrave the materials to realize 2D patterns or 3D designs.


Main Features

The CNC router bits are subjected to high pressure, high temperature, strong impact and vibration when cutting or engraving materials. So the CNC router cutter shall have certain characteristics to endure the high temperature, high speed and high cutting force situation. Some of the common features include:

  • Excellent hardness and abrasion resistance
  • High strength and toughness
  • Great temperature resistance

Classification of CNC Router Bits

Based on the tip shapes, the CNC router bits can be divided into many types and each type has specific functions. The following will give a general introduction of the types of the most commonly used CNC router bits.

  1. Flat Bottom Bits


    Such bits are also called Cylindrical Router Bits. They can engrave relying on the side edge and the bottom edge is for surface milling. The left picture shows the spiral edge flat bottom CNC router bits, which are mostly used for engraving metal and plastic material. The right picture shows the straight edge flat bottom router machine bits, which are mainly used for cutting wood materials.

  2. Ball Nose Bits


    Also called Round Nose Bits, the cutting edge of ball nose bits is in an arc shape, which could form a hemisphere during the engraving process. So, these types of bits are subject to uniform force when cutting and can cut smoothly, making them ideal for semi-finish and engraving curved surfaces but not for milling planes.

  3. Tapered Ball Nose Bits


    Also called Tapered Ball Nose CNC End Mills, they are the mixer of tapered router bits and ball nose bits. So, these bits have the characters of both the tapered router machine bits having small tips, and the ball nose CNC end mills. The tapered ball nose CNC router bits are often used for relief carving, projection carving and so forth.

  4. Corn Teeth End Mills


    Equipped with teeth on the side edges (looks like corn), such end mills are perfect for cutting hard or super-hard materials, such as printed circuit board, HDF, hardwood, carbon fiber, fiberglass, HDF composite boards, etc.

  5. Drill Bits


    This category of CNC router bits is mainly used for drilling holes on workpieces for screws. The drill bits have only bottom edges without side edges, so they can’t achieve milling work in horizontal directions except for drilling holes. They are mainly used for drilling concrete, granite, sand-lime brickwork, natural stone, soft metals, and non-ferrous metals.

  6. Three-Dimensional Irregular Router Bits


    They are a kind of tapered router end mills with a big taper angle at the cutter tip. These CNC router tools have cutter heads welded additionally on the shank. So, they are often called big head router bits. Three-dimensional irregular router bits are capable of engraving various special forms on many materials.

Common Cut Types

CNC router bits are great all-purpose tools that can be used in several applications. However, it is crucial to determine the cut direction, which can be decided by the type of material or other variables.

  1. Up Cut

    Being the most common type of cut, up cutting bits pull chips (and the material) up. When using them, the material needs to be securely held down. Upcut bits are preferable if you want to clear chips from your cuts to prevent overheating the bits. They are great for making cuts through the material.

  2. Down Cut

    Downcutting bits press the chips and the material back into the cut. Their down shear action is excellent for preserving the top surface of your material. These bits are preferable for cutting thin, flexible material but are not the best for drilling holes because the bottom layer of the workpiece will be pushed away from the bit by chips. Down cut bits leave a clean cut at the top of the workpiece but may fray the bottom edge.

  3. Compression Cut

    Compression bits (up-down bits) offer the benefits of both up and down cut bits. The bit is a standard down cut, but its tip is an up cutter. Therefore, when cutting materials like plywood, you will end up with a clean edge on both sides because the top is pushed down while the bottom is pulled up. Combining both geometries eliminates chipping and reduces the risk of damaging the workpiece.

Factors to Consider While Choosing the Right CNC Router Bit

Bit manufacturers go to great lengths when engineering their cutters, but selecting the right bit still requires some due diligence. Even though, there are plenty of factors to consider while choosing the right bit, the type of project and the material are the crucial factors – along with the brand - that you must always take into consideration.

  1. Project Suitability

    What project are you undertaking?

    Detailed work like lettering requires a V-bit (sometimes called engraving bits, V-groove bits, or V-carving bits). As the name suggests, V-bits have a cutting profile in the shape of a ‘V’. They come with different “included angles”, and this will determine what they’re used for. A 60° V-bit, for instance, will give you smaller details compared to a 90° bit, which is well suited for larger or shallower details or letters.

  2. Material Compatibility

    What are you cutting?

    Is it hard or soft wood? Is it stainless steel, fiberglass, MDF, acrylic, or aluminum?

    The material matters. It matters so much that you will find different grades of carbides used for different materials. Going for the wrong bit could be detrimental to the bit or even the machine. Plastic will require a specific bit (specifically one that will not melt it) and so will aluminum and plywood.

  3. Brands & Functions

    Except for the foregoing, you may also have to consider the brands and functions of the CNC router bits. Try to choose the CNC router cutters from formal manufacturers, because they can guarantee the quality of the router machine bits. If you buy low-quality CNC milling bits from unprofessional sellers, you may end up with a knock-off. In addition, in case you’re new to CNC engraving and looking for a multi-function bit, you can choose two-flute spiral bits since they cut a wide range of materials like plastic, aluminum, wood and foam.

Conclusion

CNC router bits are available in a variety of types, and each type has its own special processing results. So the choice of the CNC router bits plays a key role in different processing requirements. Choosing the right bits can not only achieve excellent product results but also reduce the abrasion of the tools themselves and prolong their service life.

What Blue Rhine Offers?

Being the leading supplier of CNC routers in Dubai, we offer an extensive array of high-quality CNC router bits in various sizes, designs and thicknesses, to suit the requirements of your projects. These router bits are manufactured as per the international quality standards by using advanced machinery and equipment.

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