Kaimusailing

Here is a picture of the scarf jig. You can see it has a rib on its bottom that slides in the groove in the table saw that usually has the angle guide sliding in it. The jig has a 10:1 angle with respect to the table saw blade. The jig was made with two faces, both having the 10:1 angle, one face reaches right to the saw blade when the rib is seated in the groove on one side of the blade, the other face does the same when the rib is seated in the other groove on the other side of the blade. It is necessary to cut the scarf bevels with two cuts, and the plank has to be flipped for the second cut, and the jig has to be set up on the other side of the blade. If the saw was able to cut a 5” wide plank, on edge, with one pass, then the jig could be made with only one face and all cuts would be made in one pass.
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After making the first cut, the plank is flipped over and a thin slat is inserted into the saw cut to that the plank can be clamped to the jig without the saw cut squeezing shut. I call the thin slat a kerf spacer. The second cut only has to be deep enough to cut the remaining wood left by the first cut. It takes some skill to get the second cut to be flush with the first cut. It can come out at a slightly different angle or be offset to the side slightly. The end product can be cleaned up with a power plane and belt sander. It is a very efficient way to make a scarf bevel.
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I was trying to get more consistent with the scarf bevel cuts and I finally got it figured out. I have cut about 20 scarf bevels so far, so it is about time. The first step in getting control of this technique was to always start the scarf cuts on the same face of the jig. I labeled this face of the jig “1st” as I would always be making the first cut using that side of the jig. I chose that side because I had a feeling that most of the better bevel cuts were made by starting on that side. Next I decided to use the marks that I made on the plank to line up the plank and jig. I always take a 10:1 triangle, which you can see in the picture, and mark the 10:1 angle on the end of the plank on both the top and bottom edges. Then I draw the line marking where the saw blade should begin the cut on the face of the plank. To gain consistency, I lined up the cut line with the leading edge of the jig. After I cut the first cut this way, I could see it was in a good place, just a bit offset, so I began cutting the first cut on all the bevels by lining up that mark with the leading edge of the jig.
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Next I made the second cut using the other face of the jig and now the plank was flipped over on its other edge. The mark for the cut line was placed again at the leading edge of the jig, but now the cut came out offset a bit from the first cut. This was caused by the leading edge of the jig being a slightly different distance from the blade. This scarf bevel was not too bad and could be cleaned up with a plane. Now I used the same procedure for a second scarf bevel, and on the second cut moved the cut line ahead of the leading edge of the jig by about 3/16”. This scarf bevel turned out better, but there was a discrepancy between the 10:1 angles of the two jig faces, so the two cuts were not exactly flush. Still easily cleaned up with power planer or belt sander.
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Because the 10:1 angle cut with the jig also depends on how the plank is pulled through the saw, the discrepancy can be compensated by just holding the plank a little bit outward on its way through the saw. The distance between the cut line and the leading edge of the jig also had to be increased to about 1/4”. Now the scarf bevel was nearly perfect. There is still some variability in the cuts, but by using marks and writing down notes on adjustments, the bevels are much more consistent. There are many more planks to get out and thus many more scarf bevels to cut, so getting a handle on this procedure will pay off.
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This jig was made for a specific table saw and if I end up cutting scarf bevels on another saw, I could make an equivalent jig, probably even more accurate.