Vertical CNC jig

[TmanPDX]

I thought I would share this latest jig that I created for my CNC. I am working on a piece for a client where I need to do a long finger joint (interior of a cabinet), and I really don't think this would have worked trying to do this on my tablesaw or normal router because of the length, and since I have a CNC, I thought I'd create a jig. It took a few hours to design & cut, using my CNC to get the accuracy. I am using threaded inserts to hold a horizontal piece (labeled "front" in the pic). I also offset the holes on this to give me ability to handle a wide length of woods by flipping this support over. 

When I first installed it, the height difference from one end to the other on the 26" piece was 1/32 off, which I could have probably ignored, but I put a shim underneath. I think that's decent accuracy. 

My first test pieces I didn't leave any wiggle room, cutting right to the line and it just wouldn't fit. I adjusted the next pass and took off an extra 0.005 on each of the fingers and it's snug, but can be pounded together fairly easily. It's a firm fit. I'm pretty pleased with how this works. 

Here's the jig:

   

Here's the first cut using a scrap piece of pine:

   

here's the dry fit on that pine:

   

and the final customer piece (which was lacewood). I adjusted the depth to leave it just a tad proud so I can sand it down. Got a bit of tearout. Could use a backer board to reduce that in the future, but it will sand out fine. 

   

[Cooler]

An alternative construction method:

Rip several boards to a uniform width (about 3 or 4 inches) and length.  Glue them up into a wide board with alternate pieces staggered slightly more than the thickness of the stock. When the glue-up is done it should look like a wide box joint was cut on both ends.

Repeat this process for all four boards and then join.  

No jigs required; no CNC either.  But this will only work if you are joining the ends of the boards and not the flat grain.

Nice jig.  But I think I will use my method.  

[paulJohnstoneJr]

Nice idea.

One suggestion.. when you design your tool path, cut each "slot" for the finger in 2 steps.

1. Cut from the front of the board , backwards about 1/2 way
2. Cut from the back of the board, forward the rest of the way.

Now the bit is not going through the piece of wood (which leads to tear out)

Also, I am not 100% sure, but it looks like you are using a straight bit to make the cut.
I seem to have better luck with an up-spiral bit.

Good job, not criticizing, just trying to share what I learned.

I hope this is clear.