The Scarf Cutting Jig

My variation of the scarf cutting jig is pretty much done! A little bit of cutting here, a little bit of gluing there, and after a few nights I have a completed tool ready (almost) to go to work!



and from another perspective:



My variation is narrower than the jig that inspired this effort. See Projects List

The piece of wood to be cut is clamped into the jig,



A router or laminate trimmer, fitted with a 3/4" straight bit, will sit on the carriage (the piece sitting on top of the base). The router will be pushed across the piece being cut, the carriage is moved (about 3/4") down the base, and another cut is made. These steps are repeated until the full scarf is cut. The slope of the base is 8:1, so to cut a scarf in a 3/4" thick piece of wood, 8 cuts will have to be made. (This is much easier for me to see in my mind's eye than to describe in writing!)

It occurs to me as I write this I still haven't clearly described a scarf joint. So let me try...

If you need a longer piece of wood than what is available it is possible to glue two (or more) pieced together to obtain the needed length. Gluing two pieces of 2 x 4 end to end might work, but it would be a very weak joint - if it held at all. One way to improve the strength of a glued joint is to increase the mating surfaces being glued. Another way is to reduce the angle at which the mating surfaces come together. A scarf joint is one way to achieve larger surface area and reduce the angle. Here is what a finished scarf joint should look like:



That is what I am trying to achieve with the jig, and as soon as I purchase a router or laminate trimmer (watching a couple on eBay now) I will begin testing the jig. I suspect I will have to tweak it a bit to improve the accuracy of the cuts - the more accurate the cuts the better the joints will be.