Nice. Simple and quick to make. Set the blade height to allow only a bit above the slot so the file or diamond card is at 90 to the blade. Filing a french curve card flat is pretty much a freehand deal on the small, tight radius end.
For straight cards, I have and really like using the Veritas card sharpener. You can dial in the angle to the desired angle as well as 90 degrees for flattening.
You can also buy card holders that hold that required slight curve. Easier on the old finger joints.
The more I do, the less I accomplish.
Last edited by DesertRatTom; 01-22-2020 at 10:48 AM.