CNC router bits are the most critical tools for CNC routers realizing cutting, engraving, pocketing and other processes. They determine the kind of processing you can do and the quality of your finished designs. Without them, CNC routers can do nothing. The CNC router tools fall into many types, and different process requires different tools. If your projects involve not only cutting work, but also 2D and 3D engraving, pocketing, etc., what kind of CNC router cutters should you choose? What should you consider when buy and use such CNC bits? This complete buyer guide will give you a complete introduction to the CNC router bits, including definition, classification, purposes and precautions for choosing or using them.
What are CNC router bits
CNC router bits are the tools installed on CNC routers to cut and engrave workpieces, and also called CNC router tools, CNC router cutters, router machine bits, CNC engraving bits etc. CNC router bits of different types can achieve different processes.
Based on the processing method, the CNC router cutters fall into two categories, i.e. CNC drill bits and CNC milling bits. CNC drill bits are usually used for pre-drilling holes for screws. These CNC bits drive into materials. They don’t have side edges, so they can’t mill horizontally. CNC milling bits, also known as CNC carving bits, CNC end mills or engraving router 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.
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. Such features include: Great hardness and abrasion resistance. High strength and toughness. High temperature resistance.
Classification of CNC router bits
On the basis of 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 tools.
Such bits are also called cylindrical router bits. They can engrave mainly relying on the side edge and the bottom edge is mainly for surface milling. The cylindrical CNC router cutters generally have two types based on the shapes of side edge. 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, and these CNC router bits are mainly for cutting wood materials.
Sometime they are also called round nose bits, and they have many types according to the shapes of such CNC engraving bits. The cutting edge of ball nose CNC end mills is in arc shape, which could form a hemisphere during engraving process. So the ball nose bits are subject to uniform force when cutting and can cut smoothly. The ball nose bits, therefore, are especially suitable for semi-finish and engraving curved surfaces but not for milling planes. They are perfect for routing channels in cutting boards and counter tops and to produce flutes in solid wood.
Tapered ball nose
Also called tapered ball nose CNC end mills. They are the mixer of tapered router bits and ball nose bits. So they 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.
Corn teeth end mills
This type of CNC end mills has teeth on the side edges, looking like a corn. Such end mills are perfect for cutting hard or super-hard materials, such as printed circuit board, HDF, hard wood, carbon fiber, fiber glass, HDF composite boards, etc.
This type of CNC router bits are 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 direction except for drilling holes. These bits are able to drill holes with different diameter and depth, making it convenient for the following process.
Three-dimensional irregular router bits
They are actually a kind of tapered router end mills with a big taper angle at the cutter tip. Different from common CNC router bits that the cutter head is directly machined from the shank, these CNC router tools have cutter heads welded additionally on the shank. So we often call them big head router bits. They are capable for engraving work of various special forms on many materials. The head of such CNC end mills could be in any shape, so you need to choose this type of router machine bits according to your project designs.
Major cut types of spiral CNC router bits
Spiral CNC end mills are among the most commonly-used router machine bits. They are suitable for a wide range of applications. But the cut type mainly includes three kinds, up-cut, down-cut and compression cut.
The up-cut CNC router tools clear the chips away from the material during processing. Such up-cut CNC milling bits can be used for grooving or slotting, for upward chip evacuation and best finish on the bottom side of the part. These CNC end mills are ideal for cutting relatively thick materials, but not recommended for thinner or softer materials. During processing, the upward force can pull the chips up, causing a ragged finish on the top surface, or even worse, eject the part from the table. So your material will need to be securely held down. This type of CNC router bits is used whenever the best finish is needed on the bottom side of a workpiece.
On the contrary to The down-cut type CNC router bits press the chips and the material back into the cut. They are suitable for cutting thin, flexible materials but not for drilling holes. Down-cut CNC router tools are predominantly used when a high quality cut finish is required on the top surface of a workpiece. However, it may wear the bottom surface.
Compression CNC router bits are the combination of both up-cut and down-cut CNC bits. So they have features of both these two types of CNC router tools. The bottom of the material is pulled upwards while the top of the material is pushed downwards thus eliminating the risk of damaging the laminated surfaces during processing. Therefore, when cutting materials like plywood, you may get a sharp and clean edge on both sides of the workpieces.
Choose different CNC router bits for your specific projects
It is often said that: To do a good job, an artisan needs the best tools. Choosing the right CNC router tools will help you obtain high quality products, avoid reworking and reduce abrasion of the CNC bits as well. The following text may give you a hint for choosing a right tool for a specific material.
For cutting acrylic, the single flute spiral milling cutter is recommended. This kind of CNC router bits can cut acrylic material with fast speed and high efficiency, without smoke and smell and not sticking any chips. The fine grain (or even no grain) on this CNC end mills ensures a smooth cutting surface.
For processing the acrylic surface to achieve dull polishing effect, we recommend to use double flutes or three flutes spiral milling cutters.
The double flute chip-breaker spiral mill cutter is suitable for cutting MDF, because it has two large grooves to remove chips. Besides, it can keep good balance state and will not blacken or emit smoke during cutting process.
For cutting aluminum plates, we recommend to use CNC bits for aluminum, such as single flute milling cutter. The cutting process is non-stick, fast and efficient. While for engraving small aluminum relief, the round bottom engraving router bits could be a good choice.
If you are making large size deep relief with soft wood, MDF, natural wood, PVC or acrylic, you’ll need some single flute spiral ball nose milling router bits.
For processing high density fiberboard (HDF) or hard wood, you can choose corn teeth CNC end mills.
In case of rough processing of particle boards, melamine boards etc., you can get yourself multiple tool grain milling router bits.
When making large 3D carvings, you’ll want ball nose bits that are appropriately sized for the level of detail in your model.
If you want to create lettering and or sign making, you’ll need to get a v-groove router bit. This is the only way to get a sharp grooves on your workpiece.