To choose between downcut, upcut, and compression router bits, consider the desired finish and material: downcut bits excel at clean top surfaces, upcut bits are good for bottom edges and chip removal, while compression bits offer clean finishes on both sides. [1, 2, 3, 4]
Here's a more detailed breakdown, with references:
- Best for: Clean top surfaces, shallow cuts, inlays, and visible slots. [2, 3, 4, 5]
- How they work: The flutes cut material and evacuate chips away from the shank, pushing the material downwards. [2, 3, 4, 6, 7]
- Considerations: May leave a rougher bottom edge on through cuts. [2, 4]
- Best for: Bottom edges, deep cuts, and removing material from pockets. [1, 1, 2, 2, 3, 3, 4, 4]
- How they work: The flutes cut material and evacuate chips towards the shank, pulling the material upwards. [2, 2, 3, 3, 4, 4, 6, 6, 7, 7]
- Considerations: Can leave a rougher top edge, especially with fibrous materials. [1, 1, 2, 2, 3, 3, 4, 4]
- Best for: Clean finishes on both top and bottom surfaces, through cuts, and materials with veneers.
- How they work: These bits combine upcut and downcut flutes, allowing for a clean cut on both sides of the material.
- Considerations: Can be more expensive than upcut or downcut bits. [1, 1, 2, 2, 3, 3, 4, 4, 8, 9]
References:
- https://toolstoday.com/learn/downcut-upcut-and-compression-bits
- https://www.konetool.com/upcut-vs-downcut-router-bits/
- https://www.findbuytool.com/blogs/university/choosing-the-ultimate-spiral-router-bit-up-cut-vs-down-cut-vs-compression
- https://zahyox.com/blogs/news/downcut-vs-upcut-vs-compression-router-bits
- https://www.youtube.com/watch?v=ywnRUufGuc0
- https://community.carbide3d.com/t/upcut-vs-downcut/52184
- https://kmtools.com/blogs/news/spiral-router-bits
- https://paneltools.com.au/compression-cutters-guide/
- https://www.reddit.com/r/BeginnerWoodWorking/comments/s6bu1q/34_dado_router_bit/