|Forum topic by GaryK||posted 02-24-2011 12:46 AM||9388 views||8 times favorited||29 replies|
02-24-2011 12:46 AM
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:
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:
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:
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.
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:
Both the top and bottom are cut perfectly clean.
You can also get them in a flush trim version:
So the next time you need to use a spiral but, I hope that this will help you to choose the correct one.
-- Gary - Never pass up the opportunity to make a mistake look like you planned it that way - Tyler, TX