Difficulty getting a square line around a board
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Welcome! / Forums / General Woodworking Discussions / Woodworking Methods and Techniques / Difficulty getting a square line around a board
How square is your square? Have you tested it? Try your square on a board with one straight edge, register the “handle” there and draw a line. Then flip the handle to the other side of the ruler and draw a line on exactly the same position. This test shows you, how accurate your square is. You could also measure three inches (or centimeters or even miles) on the registration face of your square and four inches on the ruler. When you measure the direct distance of these points, you should get exactly 5 inches (3² + 4² = 5², greetings from Pythagoras). You won’t ever get a line meeting itself around a board, if your square isn’t accurate. My first combination square was a cheap one from a DIY market, and on the first test, I found a discrepancy of 2 mm between the two lines at a distance of 20 cm. Further checking revealed, that the ruler wasn’t even straight, it was (still is) slightly curved. It also rocked slightly in the handle. Even heavier “engineer squares” made from steel often have small dents or notches, especially on the inside.
If you doubt your skill with the knife, try with a pencil. At least, you cannot undercut, and it won’t be driven away by harder wood sections so easily, if you pull it against the ruler gently.
And remember, that marking is not an art but a skill, and skills require practise (arts too, but additionally much more talent etc.).
Dieter
How hard are pressing the knife on your first pass?
Sometimes when making my knife lines I press too hard with my first pass and I can feel the blade of the square get pushed into my fingertips slightly the further the knife gets away from stock. I assume that the blade is flexing somehow under the pressure I’m applying.
If I do a really light pass first then it doesn’t happen and subsequent heavy passes don’t move it. Which I guess is Paul’s point as he repeats that mantra.