What’s up with the Incra jig
I recently had a conversation with a friend of mine about dovetail jigs. He understood how most of them worked, but the Incra positioning system was a bit of a mystery. Once I explained it, though, he not only got it, but he went shopping for one.
There’s two things to understand about the Incra system. One is that it is a router fence, not a jig. Like any router fence, by moving it back and forth, you control how far into the wood the bit will cut. The addition of a small auxiliary fence at 90 degrees to the main fence, though, lets you make short, through-cuts through the ends of boards (like this).
The second thing to understand is the near-perfect accuracy of the positioning system. This took me a while to figure out, but once I did, it was obvious. There’s three modes. In micro-positioning mode, you can tweak the whole thing back and forth by a thousandth of an inch at a time. You do this very rarely, usually when you’re starting of finishing a project.
The second mode is “free sliding”. Doing this, you can move the fence a foot or more at a time. Finally, there’s the most important mode, the “lock in”. When you’ve locked in the fence, it takes wherever it was when free-sliding, and snaps to the nearest 1/32 of an inch.
Think about that for a minute. You can make a cut, slide it just about 1″ away, and it will snap to exactly 1″ away. Then you can move it back to your first cut, and it will snap to exactly where your first cut was. Over and over again, perfect repeatability.
From here, the dovetails are a snap. It’s just a template that lets you free-slide to where the cuts should be, and then you “lock in” and hit the cut precisely. It’s simple and brilliant. And in case this isn’t totally clear, they provide step-by-step instructions that will give you flawless joints every time, even if you don’t understand how you got them.
Literally every woodworker I know uses an Incra now, many of them after trying mine out. You should get one too. You’ll thank me for it.
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