I generally spend more time designing and making the tools I need for a work than I spend using them for the given work.
This time, I made a quick and dirty tool in 15 minutes, that still gives a perfect result.
at least 40x25mm, 50x30 would be better
Wooden bar 2 (optionnal)
8x20mm would be fined. I used cheap solid oak wooden floor. You can also cut that from the first bar.
I did not have some, so I used cyanoacrylate (superglue)
I used both large brown packing tape and normal transparent adhesive tape.
It took less than one hour from the idea to the second build I made (I made a second build so I can take pictures to document it). Nothing to blog, but the result is exactly what I wanted: cheap, made with thing I hade available here, it solves the problem with a perfect result.
Cut a 60 to 80mm long piece of the first bar of wood (the 35x50mm one), the cut it at 45° across the middle of the 35x60mm side
Flip one of the pieces
Your cut is probably not perfectly perpendicular to the side of the bar (remember: this a quick and dirty build), and then the edges are far from being parallel when you align the pieces:
But remember, this is also a perfect build. So flip one of the pieces to correct the problem:
(Thank you God Of Geometry)
The space between two pieces of wood must be equal to the width of the groove, that is twice the depth of the groove for a 45° cut. (I want to make a V Groove in 6mm foam, so the groove will be 4mm depth and 8mm wide).