Make your Dowel Jig WORK

You don’t need to modify the jig. Just change how you use it.

Your Self-Centering Dowel jig probably has critical flaws that make it impossible to get accurate results. Maybe you blame yourself, or maybe you toss the jig. But if you ignore the instructions, you CAN get good results.

TASK “Premium” Dowel Jig

YouTube “gee whiz” product demos are great. Everything works so flawlessly! After looking around for the best possible combination of accuracy (I thought) and price, I bought the TASK self-centering dowel jig.

It’s a nice jig, better than many in this genre. But try to use it they way they show in the demo, and you’re doomed. Let’s start by examining the critical flaws that make it impossible to get good results that way.

(Some of the issues can be overcoming by drilling one hole at a time. But what’s the point of investing in a jig that gives you multiple drilling slots if you have to do that??)

Note: This article contains Amazon affiliate links. And it needs pictures to make the points more clearly. If you know of any I can borrow, send me a link. Full credit will be given to the source and to the kind soul who pointed me to them.)

Critical Problems with the Recommended Procedure

With a totally accurate jig, the recommended procedure might work. But a version you can actually afford introduces critical problems:

1. Line width
2. Movement while tightening
3. Centering

Let’s deal with them in order…

1. Line Width

Line width matters! There are nice little lines on the jig that can be seen through an opening. Those lines show where the dowel hole will be drilled, and they line up nicely with the center of the drill guide hole. So what’s the problem?

Well, there are two problems. The first is a simple matter of width. The lines on my jig are a lot wider than the .5mm pencil lead I use for precision layouts. So I switch to my wider rough-layout pencil. But does it match? Almost…

In the demo, of course, the width of the pencil line exactly matches the width of the line on the jig. (I wonder how many takes they needed to make that happen.) So I decided that I would align the left of edge of my pencil line with the left edge of the line on the jig.

In theory, that technique should work. But there’s a huge difference between theory and practice. That’s when I ran into the second problem…

2. Movement while tightening

The second problem with those lines is that the jig moves when you tighten it. You get the lines right where you want them. You carefully tighten the jig. You double-check the alignment. Crumb! The lines are no longer where you had them.

It’s remotely possible that if you do it long enough, you’ll get sufficient control of that process to get repeatable results. But we’re talking about a long time.

In the meantime, any discrepancy between the jigs position on one piece and it’s position the other means that one edge of the join is raised slightly off, compared to the other.

But the demo shows them lining up perfectly. It didn’t work for you though, did it? I’d be surprised if it did. My guess is they planed the boards between takes until they matched!

3. Centering

Let’s assume for the moment that you get the positioning problem solved. We now have the small mater of centering.

Unless the jig is perfectly centered, aligning the jig is problematic. To make the sides align, you need to register the jig against the matching face, so the small offset from center is the same on both pieces to be joined.

But then you run into the problems mentioned earlier: The need for matching line widths and the fact that the position changes when you tighten the jig.

Summary

Positioning issues produce problems with edge alignment. Centering issues create problems with face alignment. So when you try to overcome centering problems, you run into positioning problems.

Again the demo shows everything working perfectly. (How long did that take, I wonder?) Of course, if you hunt around you can find ways to modify the jig to make it center precisely. If you do it precisely. (Good luck with that. What are the odds of making it come out with the degree of precision you need? That’s pretty much the whole reason you bought the tool in the first place…)

A Process that Works

As mentioned at the start of this article, there is a better way. It starts by ignoring the “alignment lines” on the side of the jig. Let’s quickly review the requirements and go straight to the solution:

1. To eliminate centering problems we need to register the jig against the matching face of each piece in the join.
2. To eliminate positioning problems, we need to align the jig to the edge of the work, repeatably, so the holes we drill are precisely the same distance from the edge on each workpiece.
3. The solution is to make a spacer you can use to position the jig.
4. You then finger-align the edge of the spacer against the workpiece (or make a clampable version of the spacer), butt the jig up against the spacer, and hold it there while you tighten the jig.

Firmly holding the jig against the “stop” prevents it from drifting as you tighten it, so you wind up with positioning you can repeat.

Tip: After drilling, be sure to clean out the threads before loosening the jig. Otherwise sawdust gets into the works and jams things up. I use a Ryobi Power Inflator (a hand-held “air pistol”) to clean off the sawdust and small chips that collect on top of the threads without removing any of the grease.

Final Thoughts

At this point, there are two questions you may be having:

1. Is my jig precise enough to use that process?
2. How accurate is “finger alignment”?

I suspect you’re covered, on both counts…

1. Is my jig precise enough to use that process?

The process I described takes advantage of the precision that is built into the jig. When you register against the matching face, you’re positioning the** **left end of the jig on one workpiece and positioning the right end of the jig on the other.

To make that arrangement work, the distance from the left edge of the jig to the holes you drill must be the same as the distance from the right edge of the jig to the equivalent holes. But that kind of precision is practical. Expect it. (If you don’t have it, toss the jig or send it back. It’s worthless.)

It is a lot more difficult to make moving parts that precise, though. So you can expect to pay a small fortune for a jig that does a precise job of centering. But precise fixed distances are a piece of cake for modern machinery.

2. How accurate is “finger alignment”?

Finally, you may be wondering: “Align things with my fingers? How precise is that?” The answer is that the tips of your fingers are remarkably sensitive. They contain thousands of nerve endings, making it possible to feel edges that are only a tiny fraction out of alignment.

My guess is that your fingers tell the story to the thousandth of an inch. When you no longer feel a corner under your fingertips, the edges are aligned. They’re aligned so well, in fact, you probably won’t even need to sand the join. (But if you do, a teensy bit of sanding will do the trick.)

About Eric

Eric Armstrong builds yoga meditation benches, and makes them available at MeditateBetter.com. His quest for precision is motivated by his desire to make the best possible benches he can, repeatably. (If you like this kind of article, consider supporting Eric on his Patreon page.) Learn more: **About Eric (DIY’er)**