The Spline Cutting Jig
I use this jig to make all my splines. Basically it is set up to use the band saw to cut triangles out of a long thin strip of wood. It is just a board with a runner for the guide slot and another board fastened at a 45 degree angle. Cutting small pieces on a table or radial saw is a disaster. Your fingers wind up in wrong places and the small pieces fly all over the shop (not good). This is a job for the band saw! If it is done well the splines will look like this…
A quick word about fit: Once you have cut a strip of wood to approximate size let’s say 1/4 inch thick by 1 inch wide by 18 inches long, you fine-tune the fit with the planer so that this strip will easily, but barely slip back and forth in the spline slots you have cut in the box. If you make this fit too tight you will have to fight the work and pound the splines into place in the slot. A slip fit lets the splines and wood swell a little with the glue. A thin bit of glue will not show, but a spline that doesn’t bottom out in the slot looks really bad when the box is finished.
Since splines are often made from expensive and rare woods, I try not to waste any of it. Why make a square spline for a triangular slot? So as you see in the picture you use the jig to cut a 45 across the strip and then FLIP IT OVER and make your next cut forming a triangle. The width of your strip really determines the size of the triangular spline. If you need a smaller spline, make your strip more narrow. Don’t try to cut smaller 45s it just doesn’t work. I usually push the strip a little beyond the blade before making the second cut so I get a flat spot at the point of the triangle. I use the flattened point to push the splines in place. It is easier on my fingers.
Any scrap will do when you are experimenting with a jig, but when I have perfected a jig I try to make a pretty one. It makes time in the shop more fun, and I can take pride in using it. This one is made from a scrap of bird’s eye maple and eucalyptus veneer.
This jig works better if it is thicker and allows the triangles to fall when cut and then be pushed slightly out of the way by the jig after you have cut through the strip. Don’t push too hard as you cut, let the blade do the work. Pushing makes the triangles fly and you want to keep the triangles on the table of the bandsaw. The rough edges of the bandsaw cuts don’t matter. You will just trim off the excess sticking out beyond the box edges with the bandsaw or sander anyhow. I use the hole in the end to hang the jig on the saw between uses.
Later I’ll show more about splines. Have fun, and keep boxing.
-- Big Al in IN