Upcut Vs Downcut Router Bit | Comparison | What’s the difference between the two?

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When it is to create a project par excellence, then appropriate selection of tools is critically significant. Also, to get a desired finishing, it is important to check on the tool life and it’s cutting speed on the specified workpiece. The tooling producers go deeper in engineering the tools so that they can deal with the properties and special aspects of the work material. Therefore, proper selection of tools is very important before starting a task, which eventually determines the project’s success or failure.

In this post, I will discuss the upcut and downcut CNC router bits while substantiating their differences. So, stay online.

Upcut CNC Router Bit

Upcut spiral router tools are quite a trend among the most widely used spiral flute-type tools. If your project requires machining procedures like slotting slotting grooving, then go use the upcut bit for upward chip clearance and get a fine finish at the bottom side of the workpiece. You can do rapid cuts with upcut router bits since the tool evacuates the chips from the workpiece. Upcut geometry is typically used to get the best surface finish at the bottom of the workpiece.  

Note: Do not use upcut router tools for cutting thinner materials but only thicker. Doing so might result in a ragged finish surface at the top of the material, or worse ejecting the workpiece from the router table. 

Downcut CNC Router Bit

Downcut spiral router tools are popularly used to cut thinner workpieces that can be moved down into the CNC router bed than being uplifted using an upcut bit. This type of spiral bit is fit for routing while using vacuum workholding technique where the seal maintenance between the machine bed and the workpiece is crucial. These tooling bits are commonly used when you are particularly looking for high-quality finish cut at the top surfaces of the material. 

Downcut CNC Router Bit

Downcut spiral bits often need limited cutting speeds, otherwise the chips will be held back into the work surface. Chip clearance with a downward spiral bit is less effective than an upward tooling bit.

Difference Between CNC Router Upcut Vs Downcut Bit

The primary difference between an upcut and a downcut CNC router bits is the flute’s direction. In case of an upward bit, hold the tool shank, pointing it straight down as if you want to plunge cut into the material surface by rotating the tool in clockwise direction. On the contrary, with a downcut bit, hold and rotate the bit shank counter-clockwise to drill the material surface.

But the question is how to understand how would you know which bit is fit for which task? An upcut CNC router bit is efficient in clearing chips out of the cut, leaving a finely finished bottom surface of the workpiece. However, the top surface of the material will be rougher (or any side through which the bit enters the material). The opposite happens in case of using a downcut bit into the material surface. That is you will get a clean top surface but a rougher finished bottom surface on using a downcut bit into the workpiece.  

Downward bits are also ideal for cutting rabbets, shallow dados, and visible slots since it gives a cleaner finish along the edge of the groove or hole. 

Note:  Make sure to keep a slow feed rate of the downcut bit, allowing more time to remove chips while cutting grooves or dados. 

How to differentiate between Upcut and Downcut?  

First of all, check for the right bit side (it does not matter if the face of the tool-tip is upward or downward. Next, you need to check out at what direction the flute direction is moving as the bit goes around to backward. Check if the flute is heading up while cutting around the right side of the tool. If so, then what you are checking at is an upcut bit.

Second of all, hold the router bit manually with its tip pointing down and away from yourself. Rotate the router tool in clockwise direction and observe the reflection of light falling on the bit. If the reflection of the tool moves up on turning it, then the bit you are testing is an  upcut bit. Conversely, if the reflection is moving downward as you rotate the bit, then it is a downcut bit.

Note: If the flute is twisted towards right till the tip of the bit, then it is an upward bit. Contrarily, if the flute is twisted towards left till the tip of the bit, then it is a downward bit. 

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