I have never had a chance to use a finger joint bit on the router, and since I picked one up some time ago, I would like to know how it works. It was on special at a tool store I deal with and being sold "as is" because the box was open and of course there were no instructions with it, and I don't even know if it even comes with instructions, or like most router bits you figure it out on your own. The one I got was the Freud Finger joint #99-037  I had it in my mind that this must be a simple bit to use so my first idea was to have 2 pieces of wood of exactly the same width and run them through the bit one face up, the other face down and see what that would do.

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Well ... as it turns out, nope, that wasn't how this bit worked, then I wondered if it was the height that I had the bit at, maybe that had something to do with it so I raised the bit slightly to expose more of the base ... 

 ... Nope, that didn't work either and I somehow suspected that was not the solution. 

As I looked at the 2 joints, both together and apart, I noticed that in the offset, one of my pieces of wood was a half-finger joint tooth higher than the other side when they aligned. That gave me the clue that the bit actually needs to make passes through the wood at 2 different heights. 

Finger Joints

I had 2 choices, I could either raise the router in the table by half a tooth height, then probably have to make multiple small adjustments and re-tests to make sure it is set correctly, OR I could raise the wood above the table by inserting something like some veneers under it to get the correct height. I could tell by the cuts I already made just how high I needed to go and the first thing that came to mind ... was maybe I have a thin piece of plastic sheeting that will fit that depth. I gathered together a few pieces that I had, and finally found one that looked like it was a perfect fit ... now to try it.

Finger joint router bit

The results were about a perfect as you can get. The joint came together perfectly with an almost perfect alignment on the top and bottom, at least nothing that a few swipes with sandpaper would not fix.   The height of the plastic I was using turned out to be .09 of an inch or  11/128th of an inch or 2.3mm  .. probably a standard size from most plastics suppliers.  I had 2 pieces a small 3 x 5 inch that I could use for end cutting, I also had another piece that is 3 inches by 10 inches which could easily be used for longer cuts. 

Finger joint

This also got me thinking about what you could do with this bit future decorative cuts. I would make some very attractive breadboard ends for cutting boards .. or even table tops. I could easily be cut up and used as pieces for decorative banding ... there are lots of different applications for this bit, but if all you want to do is make boards longer ... it works great for that too.

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Copyright Colin Knecht

How to Make Finger Joints