I did my measurements with a digital angle meter so thought them to be accurate. Your post based on the penny measurement suggests I am off by quite a bit. Not liking being off by quite a bit
and having some spare time, I thought to confirm the digital meter and the penny trick with some math. Heres what I got.
The math for angles is a bit of a pain if one is not into math, which I am not, so I used an online calculator to calculate the angles. The one I used is here.http://www.endmemo.com/geometry/triangle.php
I started with the penny trick which says 1 - 2 pennies under the spine should give 10 to 12 degrees.
So I measured 2 pennies to give it a best case scenario and got 2.75mm of thickness.
I measured the depth of the blade mid way down the blade and got 45mm.
I measured the thickness of the spine mid way down the blade and got 1.25mm.
So the calculation peramiters are.
Two lines of 45mm separated by two pennies at the spine edge, 2.75mm, plus half the blade thickness at the spine, .62mm bringing the total separation to 3.375mm.
The calculator says the angle is : 4.2982 degrees.
This did not match your angle, so I though maybe if the pennies where pushed under the spine the full width of the pennies. What would that give?
I measured the diameter of the pennies and got 19mm. If I subtract 19mm from the 45mm blade width I get 26mm.
Inputting the new length of 26mm into the calculator I get 7.4427 degrees which still doesn't match the penny trick by more than 20%.
So I moved on to confirm the digital meter. I measured the knife as above and took digital readings of the angles. They matches the math pretty perfectly, so I am thinking my use of the meter and the math is likely okay.
So whats the deal with the penny trick which is wrong by more then 20% given a best case scenario? For it to be accurate, the knife would need to be thicker or shallower, or both.
Anyways, it was a good exercise and I learned a thing or two doing it. Many thanks