Rail coping sledge
thingiverse
It's a well-known project based on a rail coping sledge jig. See the video to learn how it works. This design is inspired by Rockler's jig. I used clamp pressure from Uni-Max, available at https://www.uni-max.com.pl/pl/produkty-pl/obrobka-drewna/sciski-i-stoly-stolarskie/dociski/docisk-gh-225-d. The next essential component is a jig from Axminster, found at https://www.axminster.co.uk/axminster-148-piece-jig-making-set-950114. You can substitute this with an M6 screw, but be sure to grind it first.
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