There are way too many options out there in the market, and it’s hard to pick the right spiral router bit for your project, and the concept of upcut vs downcut might confuse beginners. The one that troubled me the most at the beginning was figuring out the differences between these router bits, and which ones to choose from for my projects.
In this article, we will discuss the scenarios that they should be used in, and what distinguishes upcut, downcut, and compression router bit.
Upcut router bit is a perfect choice when you try to achieve a smooth finish at the bottom part of your material. This type of bit would pull wooden chips upward from the material, allowing for maximum chip evacuation during cutting. One biggest advantage is that due to the high evacuation rate, you would be able to run the bit at a high feed rate, without having to worry about heating up the bit or heating up the material from friction.
However, this might cause some frayed edges, but it’s always easy to deal with by sanding. If the top side (the side that the bit enters) will not be visible for your piece, employing an upcut router bit is still a great option. It lets you use a quicker spindle speed, allowing you to finish the job faster.
A downcut router bit would do pretty much the opposite of an upcut bit. If the top side of your workpiece is important and going to be seen, then we recommend using a downcut bit. The downcut bit pushes material away from the surface, and into the machine bed, rather than being lifted with an upcut bit. This can become a big issue on some deeper profile cuts, because the wood chips are can’t be evacuated properly. That causes the bit to continuously recut the same chips, resulting in excess heat and increased wear on the bit. And that’s why a lower spindle speed is necessary, and we recommend it more than other thinner materials.
Because of the smooth finish, it provides on the top cut edge of the hole or groove. Downcut bits are also ideal for cutting shallow dados, rabbets, and more visible slots. When cutting dados or grooves with a down cut bit, you can reduce the feed rate to allow for extra chip removal time.
Upcut vs Downcut, What’s the difference?
One of the easiest ways to distinguish upcut vs downcut bits is to look at the direction of the flutes. Look for the right side of the bit (doesn’t matter if you hold the bit upward or downward). Next, look at the direction of the flute is going while the bit rotates rearward. Check to see if the flute is going up as you cut around the right-hand side. If that’s the case, you’re holding an upcut router bit. If it goes the other way, it would be a downcut bit.
On an upcut bit, if you point the bit straight down on the surface, just like if you are going to plunge cut into the workpiece, you would be able to drill into the wood by spinning the upcut router bit in a clockwise rotation.
With a downcut bit, you would need to turn it counter-clockwise to be able to drill into the surface.
A compression bit may be particularly beneficial when a smooth edge is required on both sides of the material. As both flutes meet, the top end of a compression tool will give you a downcut, while the bottom end will give you an upcut, creating compression. The upcut side of this tool is used to draw the chips out, while the downcut side is used to polish both edges. When cutting doors for a home, for example, all of the edges of the door slab are visible, thus a compression tool would be the best option of the three.
Further watch: https://www.youtube.com/watch?v=hTlx3FH39Bs
Read further on how to choose your router bits here: Complete Beginner’s Router Bits Buying Guide