Panel Glue up Question

Question

I apologize for this elementary question, but I'm just getting started with woodworking. I'm working on my first panel glue up - made of 1x6 walnut. I'm wondering how "square" the edges of the planks have to be in order to get a seamless joint. I'm asking because I bought the wood rough sawn and bought a nice track saw to straight-line the edges. I don't have a jointer so I was hoping by buying a nice track saw that I could get joint ready edges off the saw. What I'm seeing is that saw must be riding ever so slightly crooked in the track because when I check the edges of the planks with a combination square, there is a very tiny sliver of light I can see on one side of the edge. It's really a sliver as I have to shine a light behind it to see it. The edge is consistent throughout the length of the board. Is this sort of thing normal and considered to be within the tolerance of a nice track saw? Will planks that are just ever so slightly out of square pull together with clamps?

Since I've never done this before, I'm not sure if I'm being too much of a perfectionist or if there really is cause for concern.

I think this might be happening because the weight of the saw wants to "fall off the edge" on the side of the saw making the cut. I might be able to resolve this by figuring out how to get a more stable base to work from as I was trying to use the garage floor which isn't the easiest to work from.

Thank you for any insight and/or suggestions.

Answer 1

In general, panel glue-up requires accurate square faces on the boards being glued. However, not all is lost.

One possibility is that your combination square is not perfectly square. To try and verify this, cut several thin strips of wood using your saw. When pressed together (in the same orientation as they were cut, see below for why) any deviation from flatness should be more apparent. If the strips form a flat surface then perhaps your combination square is at fault and not the saw.

If the saw is indeed not cutting perfectly square, you still have some options:

One option is to tune your track saw to get perfectly square cuts. Perhaps your theory is correct and the way you hold and move the saw causes the saw to cut out of square. Perhaps your technique is okay and the saw's 90 degree stop is not perfectly accurate. Either way you can try and adjust the bevel angle of the saw. Perform the alignment by doing test cuts, not by aligning the blade to the sole of the saw.

Another option is to keep the saw cutting as-is, and simply flip the boards as you glue the panel. In this scenario, if your cuts are 89 degrees instead of 90, flipping every other board will give you an angle of 91 degrees, resulting in a perfectly flat mating surface. To make sure you are flipping correctly, mark the top (or bottom) part of the wood you are cutting, so that you will be able to later place the boards for the glue-up correctly.

Here is a greatly exaggerated illustration of the problem you seem to be facing:

And here is is with the middle board flipped:

Finally, you can align the cuts in such a way as to have the angles complementing. Again an exaggerated illustration:

Answer 2

To get a flat panel, you usually need to start by jointing the glued edges to be extremely straight and perpendicular to the reference face of each board, and then plan on planing, scraping, and-or sanding the glued-up panel to remove any alignment error that happened during glue-up.

Remember that as it gains and losses moisture (and swells/shrinks acroos the grain as a result) it may not want to stay completely flat; if you are attaching it to other things you need to allow for possible wood motion of this sort. Wider panels, like wider boards, will have more total motion than narrower ones.