Grinds, why?

Sharpening restores the original edge angle. This scheme shows sharp and dull wedge shaped and hollow grind blades, and a yellow sjablone indicating the restored edge angle.

The dark parts exposed by the sjablone represent the volume of metal to be removed during sharpening. This is smaller with hollow grind than with wedge shaped blades. This proportion remains constant during the life of a razor. Therefore, client-level sharpening of hollow grind razors is easier and faster than of wedge shaped razors. Hollow grind razors are more expensive than wedge shaped razors, because the production process is more complex. However, the quality and the degree of sharpness are principally equal in both types. Only their purposes differ, which is treated in later chapters.

Hollow grinding reduces the real cutting angle. This reduction A compared with the straight edge angle B at a blade thicknes X and a wheel diameter Y can be calculated as follows: sin A = X / (Y x sin B).