Reinforce miter joints using splinters

Circular saw spline jig

After the fail when I tried to reinforce with dowels the miter joints in the corners of this cabinet door, I thought I could try to cut grooves in the corners to glue some splines to reinforce those 45 degree joints. Typically, one makes a table saw spline jig, but I didn’t want to make one at this moment, so I decided to try this system using my hand held circular saw. A kind of spline jig.

Luckily, the apron rails I used when I made my workbench frame are quite wide, and one of the apron rails is flush with the table top edge. So, there I can put my cabinet door vertically with the rails and the stiles at an angle of 45 degrees to the table top. And that is the spline jig for circular saw that I made.

Circular saw spline jig for circular saw

It was easy to hang the window with nails. Then I put a strip so it is up against the window. This strip is to give more base to slide the skill saw and to guide the skill saw fence. In the video you can see that I need to push the fence against the strip of wood.

Marquetry sheets I've glued inside the grooves

I think it would be better to use solid wood to make the splines, but I didn’t want this to get complicated, so I used some marquetry to cut the splines I need to insert in the grooves to reinforce the miter joints.

It is easy to set the depth of cut in this spline jig (I am not sure how deep I should cut this grooves. May be I cut them too deep), but one needs a steady hand and some patience to adjust the width of the grooves. If the spline and the disc of the saw are the same thick, then there is no problem. But in my case I had to set three times the saw fence in order to adjust the width of the groove with three cuts.

Gluing the sheets inside the grooves in the miter joints
How to reinforce miter joints

The result, being the first time I cut with this kind of skill saw spline jig, was quite satisfactory. Now I just have to glue the splines (don’t put too much glue in the splines and inside the grooves), let it dry overnight, use a tenon saw to cut the protruding parts of the splines and sand until they are flush and nice.

How not aligned dowels look like

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