Who said there was no such thing?? If you need a longer board don't go down to the lumber store, SCARPH one!
Two boards being scarphed together.
According to the U.S. Department of Transportation, Federal Aviation Administration's Airframe &Powerplant Mechanics Airframe Handbook, AC65-15A (a little dated but still valid) when scarphing structural members in aircraft, "The slope of the bevel should be not less than 10 to 1in solid wood". Well if it's good enough for aircraft repairs, it's good enough for me.
This is a a scarphing jig set to a 10 to 1 slope. It is based on a plan found in the June 2004 (Vol. 60 No. 3 Issue #233) of Workbench magazine. That plan specified a 8 to 1 slope. So I changed it to 10 to 1, made it wider, and reinforced the router sled so it would not bend over the larger gap between side rails..
The bit is a 1/2' straight bit. The depth is set to just touch the end of the bed.
First I roughed the slope on the band saw, and then after clamping the board to the bed trimmed off the excess. You can see the result. This jig makes very consistent slopes and leaves the surface perfect for gluing. Not too smooth, not too rough. You may have noticed that the router bit has taken out some material on the side rails. The jig is set up that way, so that the piece is trimmed cleanly side to side.
The gluing jig is a counter top sink cutout, ripped and rejoined at 90 degrees. I'm hoping the nice flat surfaces will help in keeping the boards being scarphed aligned. You can see more boards to be added to the one in the jig. The pressure board is a length of Oak that was salvaged from an old pallet.
There are 3 scarphed joints in this photo. After doing all the scarphs, I'll run the board through the planer, and the joints should all but disappear
I'm trying to make a couple of 2 1/2" x 3/4" x 16' planks out of scrap chunks of 2x4s that I got by dumpster diving at a local construction site.
If you give me money, I'll try to spend it.