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What the heck is a compression router bit?

37K views 30 replies 23 participants last post by  FHG1 
#1 · (Edited by Moderator)
This is mainly for the members that are relativity new to woodworking.

Most all of us use a router and one type of router bit is a solid carbide spiral bit.

Did you know that there are more than one type?

Here's the most common one:

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It looks just like a drill bit (minus the point) right. This is called an UPCUT bit. It's called that because it forces the chips up away from the tip of the bit.

Here's a DOWNCUT bit:

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Like the name implies it forces the chips down toward the tip of the bit.

Why would you choose one over the other. Well the upcut bit is good for blind holes where you want the chips to be removed out of the hole. The only problem with this is that same upcut motion can also cause the top surface to splinter up creating a messy hole.

If you were using the same bit on the edge of a piece of wood the bottom edge would be nice and clean because the "up" shearing action of the bit. But again the top edge might be splintered.

With a downcut bit you would have the opposite problem. The top would be clean and the bottom might be splintered.

Downcut bits are great for cutting dadoes. The top edges will remain clean.

As you can see they both have their good and bad points.

How would you like to have a bit that will allow the top AND bottom surfaces to be splinter free?

Try a COMPRESSION bit:

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This gives you the best of both worlds. The part of the bit closest to the tip is upcut and the other end is downcut.
That is why it's called a compression bit. It compresses the chips into the center of the bit.

It's great for cutting openings in wood.

This makes it especially great for plywood, laminates and MDF when you need both the top and bottom edges clean. You just have to make sure that the piece of wood you are cutting is thick enough so that both ends of the bit have room to work.

This is the bit I used to cut the inside and outside of the rings on my cutting board:



Example of the setup for cutting the inside circle:

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Both the top and bottom are cut perfectly clean.

You can also get them in a flush trim version:

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So the next time you need to use a spiral but, I hope that this will help you to choose the correct one.
 

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#9 ·
I was in my local Woodcraft store recently when a fellow came in and asked a salesman for a compression bit. Plans he was working from called for such a bit. The salesman had no idea what he was asking for and the customer didn't know how to properly express what he wanted. The customer had already looked at bits prior to speaking to the salesman. He explained that he saw upcut bits and downcut bits but no compression bits. I opened my big mouth and explained that a compression bit is a combination upcut and downcut all in one. The salesman spoke to the manager who eventually came out and said we don't have any in the store but I can order one for you. I guess knowledge of them is not too great and perhaps that keeps demand for them down. Either that or as mentioned above, the price. At any rate, nice tutuorial on spiral bits Gary.
 
#21 · (Edited by Moderator)
Well, I stumbled onto this... My jaw dropped!

... for almost $80, I think I will pass on this one… until they get more reasonable! LOL

Hey I also found them HERE for a little more reasonable prices!

Still… very pricey for me…

Nice to know they are around… though…
 
#22 · (Edited by Moderator)
Joe - you can get a 1/4" Whiteside bit from Woodcraft for $36.

That should handle most all of your needs.

Freud bits are expensive.

You will pay almost the same price for a regular up or down cut solid carbide bit.

Spiral bits give you a lot better surface and cut a lot easier than a straight bit. The easy cutting will make them last about 10 times longer. It cuts with more of a shearing action vs the slapping action of a straight bit. Plus if you don't mind them being undersized, you can get them resharpened.
 
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