This is not a review of the Incra Ultra. It’s awesome, there’s nothing to review. If you like precision and repeatability go get one. To call it a jig in an injustice. Sure it comes with templates that make dovetails and other decorative joints easy, but it’s much more versatile than that as you’ll see in this post.
For this post I’ll take you step by step in making a decorative box with simple box joints, a rabbeted box top and “router whittled” handle that attaches with a loose tenon. This is also my 1st attempt at bottom inserted in a stopped dado. I’ll also go over some “hard learned lessons” from using this thing over the last few months. Let’s get started.
Here’s the raw material. A ½” x 3.5” x 2’ piece of poplar from Lowes. These pieces are cut VERY precise and if you hunt you can find some good grain patterns. I cut 4 pieces 3.5” long (this is going to be a cube) and mark the inside tops of the box. I’ll keep everything in order so the grain flows from side to side on the final box:
I’m going to make the box joint cuts ½” x ½” to stick with the cube theme. For that I break out a ½“ upcut bit:
To set the bit height I use two pieces of stock. For box cuts you want the height a hair (1/64” - 1/32”) over the stock thickness. You’ll see why later:
Next I set the initial fence setting. For this I use a piece of brass square stock:
I use the micro adjust feature to make the bit flush with the fence. Each line on the dial represents 1/1000”:
Once that’s set I lock the fence and move the ruler to read -½” on the scale indicator.
Then I set the fence to 0:
This gives me the location of the 1st cut (½” bit sticking ½” out from the fence face).
Next I set up the 90 Deg jig that comes with the Incra Ultra package:
HARD LEARNED LESSON #1
Adjust the nylon screws on this jig as tight as possible with still being able to slide the jig. On my 1st box joint attempt these screws were too loose. This resulted in play and very loose fitting joints:
HARD LEARNED LESSON #2
Always test your set up on scrap. When making a joint for the 1st time go all the way through and complete one corner. You’ll practice the speed of feed and make sure everything fits well. Here’s the 1st cut in the test piece:
HARD LEARNED LESSON #3
After making the cut all the way through the material STOP and shut off the router. Wait for the bit to stop spinning then back the piece away. This will prevent the bit from making multiple cutting passes. Even with a tight set up this will introduce some play in your joints.
Now it’s a matter of moving the fence over in 1” increments and repeating the cut:
BTW the ultra comes with many templates that allow for easy cutting. The fence setting of each cut are marked with red and blue lines (a and b cuts). But for simple joints I find the ruler is just as easy to use.
When cutting out material at the end of a board it’s best to take a few passes at it:
And that’s side a done for the test piece.
For the mating side b I make the 1st cut with the fence setting at ½”:
Just like before I move the fence 1” at a time and repeat the cuts:
And here’s the test joint put together. The fit is tight and right. Also you’ll see how the pins stick out by that hair that we over adjusted the bit height by. This is done on purpose so we can sand everything flush later: