Difference and Uses: Down cut, Upcut, Compression bits

cnc router tools

Based on the direction of the spiral flutes, CNC router bits can be classified into up cut, down cut, and compression router bits. These three kinds of router bits are all made of carbide and are extensively used in woodworking. So, what are their differences and when should they be used? This article outlines the four key differences between them, aiming to clarify any confusion you might have.

cnc router tools

  1. Different Flute Directions:

Hold the router bit by the shank, with the flute facing downward, and observe the spiral direction.

Up cut spiral router bits

Down cut spiral router bits

Compression spiral router bits

  1. Different Chip Removal Direction And Cutting Performance:
  • Up cut spiral router bits:  the chip removal is upward. The flying wood chips will hit the top surface of the workpiece, which causes the top surface of the workpiece to be relatively rougher than the bottom surface, and the bottom surface is relatively clean.
  • Down cut spiral router bits: the chip removal is downward. Wood chips hit the bottom surface of the workpiece, resulting in a relatively rougher bottom edge compared to the top edge, which remains cleaner.
  • Compression spiral router bits: chip removal in the middle of the board, leaving both the top and bottom surfaces clean.

Up cut router bits

Down cut router bit

Compression router bits

  1. Different Cutting Materials:
  • Up cutting router bits are well-suited for cutting non-laminated boards, such as solid wood, where the processing requirement only needs a good surface finish on one side.
  • Down cut spiral bits are especially suitable for cutting thin boards, such as man-made boards and solid wood boards. Because the thin boards are not easy to vacuum on and fix, the down cut end mill can utilize the force of downward chip removal to firmly secure the panel to the worktable, preventing it from moving during cutting.
  • Compression CNC router bits are suitable for double-faced laminated boards, such as MDF(Medium-density fibreboard), plywood, and chipboard, which are artificial wood products. They can achieve a good surface finish on both the top and bottom of the board. However, please note that the spiral compression router bits are not suitable for cutting solid wood.

woodworking tools

  1. Different Price.
  • CNC router compression bits are relatively more expensive. This is because they are mainly used to cut double veneer. These panels are laminated with melamine, which is brittle and hard, and the chips build up in the middle, causing high heat. Additionally, you need to cut through in a single pass. This requires a better quality of carbide for the tool.
  • The materials used for spiral down cut bits and spiral compression bits are the same. However, the manufacturing process for downcut bit is relatively simpler, making them slightly cheaper, although the overall price difference is not significant.
  • The most economical option is the spiral up cut bit, which is the most commonly used.

wood router bits

Compression CNC router bits

Each of these three router bits has its own set of pros and cons, so there’s no one-size-fits-all choice. It’s crucial to select the right CNC router bit based on the specific processing scenario and material.

 

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