Thread: How do not make it worst?

Originally Posted by straightrazorheaven

An simpler formula to calculate your bevel angle is

a=2(tan({0.5x]/y})

a = bevel angle
x = spine width
y = blade width

tan() gives the ratio of two side lengths. That formula cannot output an angle. At the very least it should be arctan.

However, while the tan-based formula may be simpler to calculate in theory, it is not the simplest to calculate in practice. In practice you measure the hypotenuse - from the edge of the razor to where the hone would touch the spine.

Your assumption that y is the side adjacent to the half-bevel angle is fine, but basically impossible to measure since you would have to measure inside the spine itself. In reality the hypotenuse gets measured, hence arcsin is used for calculation.

I would also like to point out that in the original forumla given by Glen earlier in this thread, the assumption is that the resultant angle produced by the arcsin function is in radians, and is then converted to degrees via multiplication by 180/pi. If your calculator is in degrees mode, the formula should not include this conversion factor.

I'd also argue that you need to be very careful with definitions of variables: h is the hypotenuse - the distance from edge to honing flat on top of the spine - in that formula. If you take the actual height (back of spine to edge) for most razors you will be mis-measuring.

James.