I figure that you want the staple to be perpendicular to the force of the paper to that the tearing action is spread out over the area on the paper. In that regard, for a top-left staple, it makes sense that the 45* is a good rule of thumb. I am looking at a handout right now, What’s New in Zoning Law?, and it is stapled vertically at the top left. To minimize the stress-to-area ratio, I will have to fold the paper vertically down the left hand side of the page–as though I had run a series of staples down the left-hand side creating a crude book.
When I turn this handout in a more normal, for lack of a better word, fashion, all the tearing stress is focused at the bottom point of the staple, meaning the stress-to-area ratio is very high, IMO, and the paper should tear more readily. Supposing instead that it were at an angle, then that stress would be spread out over a greater area, and the handout’s life will be extended.
Okay, now everybody pull out some stapled stacks that you have used before thinking about this question:
What are the ratios of the distance between the left edge and the top fold, and the top edge and the side fold. For example, my Township Law 101 packet folds 20mm from the left edge and 35mm from the top edge, thus creating a right triangle where the hypotenuse is the line along which the paper is folded and I go from one page to the next. I assert that the optimal angle of staple is parallel to the hypotenuse (however that is spelled).
Let’s check for consistency: 30:55 for What’s New in Zoning Law.
Appendix E gives me 23:30.
I’m not good at trig, I can’t speculate what angles these give for the hypotenuses of these triangles. It is my hypothesis that whatever the average angle is will be the best angle for optimal stapling.
The depth of staple would depend on the thickness of the stapled material, wouldn’t it?
Anyway, what I really wanted to say is this: Chairman Pow, I very nearly Pitted you for dropping this bomb and not telling us more about it: