Splined Edge Joint

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Edge Joining with a Spline.....

(or how to join two boards without dowels or biscuits!)
12/99

It's really quite simple to take narrow boards and glue them into wider boards. And you don't need a bunch of fancy tools. You will need your table saw, some bar clamps and some C clamps.
Here in this pic, the joint almost disappears. You can see the spline still sticking out of the glue-up. The first thing you'll want to do is spread your boards out and try to match the grain the best you can. Mark your pieces and then either run them thru your jointer or table saw. I don't have a jointer yet, but my table saw works fine for glueups under 4' long. I usually glue up 3/4" stock in pairs, saves in assembly time and provides more even clamping pressure.

Lets give it a try!

I also try to make sure that the glue up is wider than I need, at least 1/8" per side. This is because the clamps will dent the edge of your assembly. If this isn't possible, then be sure to put some scrap stock between your glue-up and the clamps!
After you have the joint side of your pieces ready, you can start the groove. If your using 3/4" stock, then your spline can be 3/4" also. This means the groove in each piece will need to be 3/8" deep plus a little room for the glue to squeeze out. I usually add 1/32" to the depth, hardly notable.

Don't worry about how wide to make the groove, it doesn't matter. We'll make the spline fit the groove.

Set up your rip fence so the blade is somewhere near the middle of your stock. Secure a feather board in there to keep the stock from wandering! Now run the stock thru the blade, turn the piece "end-for- end" , and pass it thru again! This guarantees the groove is right in the middle of your stock. Do this to all your stock, then we'll cut the splines.
The yellow thing is my feather board, from Woodworkers Warehouse. It clamps into the groove in the table saw.

Now that the grooves are done, measure the gap, and run some test pieces for your spline. You want it to fit snuggly, by hand. Not too tight or the glue will be scrapped off completely. But let it offer some resistance. Once your satisfied, run your splines out of the same stock as the boards.
Remember!!! Use a push stick!!! Save yer Fingers!

The following few papragraphs were submitted by Brian Hale After I cut my spline I use a small backsaw, or dovetail saw, to groove the flat surface of the spline. I stroke the saw 3-4 times at several places on both the top and bottom of the spline, just deep enough to make a small groove. I then glue the pieces and assemble the parts.

As I'm drawing the parts together with the clamps, I stop just before the seam is closed and allow the glue to disperse. Any excess glue will work its way through the small, saw cut grooves and into the seam. I'll then do the final tightening.

This method is especially useful when polyurethane glue is utilized. Since this glue expands to fill gaps more the yellow glue, it can cause the joint to be more visible.
Another tip is to put masking tape on the top and bottom of the boards at the cut edge just before making the cut on the saw. Then when the glue squeezes out of the seam it dries on the tape and not the wood. This makes clean up less time consuming and assures an even finish when staining.
Thanks Brian!

The two pics above show how I clamp the assembly. Remember there are two glue-ups here. The only thing which is really important is that the glue-ups are exactly the same total width, since they're pressed one on top of the other. I spread the bar clamps out 8-10" apart and use C clamps with hardwood scrap to hold the assembly flat. Also...make sure you put waxed paped between the glue-ups and also between the scrap pieces. Don't apply too much pressure to the bar clamps, but you do want a nice even bead of glue to squeeze out the seam. This is easily removed with a scraper afterwards. Please, don't use water to wash off the excess glue. That delutes the glue and washes it into the pores of the wood, causing problems later when you try to apply a finish to your project.

Here are the pieces the next day. Scrape off the glue and give it a quick sanding and your all set to make anything that requires wider stock. I've used this method for years and never had a glue line fail! Give it a try, and let me know how you make out!

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