Sharpening

Modern synthetic grinding wheels and flat sharpening stones can be manufactured in precise grades of abrasiveness according to the intended process.

Very sharp knives sharpen at about 10 d.p.s (degrees per side) (which implies that the knife's edge has an included angle of 20-degrees).

For an extremely durable edge, a machete, chisel, drawknife or ax should be sharpened down to 30° – 40° providing even more ruggedness and longer lasting sharpness.

Sharpening a straight edge is relatively simple, and can be done by using either a simple sharpening device which is very easy to use but will not produce the best possible results, or by the skillful use of oil or water grinding stones, grinding wheels, hones, etc.

Sharpening these implements can be expressed as the creation of two intersecting planes which produce an edge that is sharp enough to cut through the target material.

The edge may be steeled or honed by passing the blade against a hard metal or ceramic "steel" which plastically deforms and straightens the material of the blade's edge which may have been rolled over irregularly in use, but not enough to need complete rehappening.

Examples include: A number of blade sharpeners operate a mobile business,[1][2] traveling to their customers locations, often in highly equipped vehicles.

Still very common in many areas of the world, skilled craftsmen provide a roadside sharpening service for kitchen knives and cleavers, scissors, and sometimes other blades.

They commonly have a 'round' which may include trades such as butchers or barbers some of whom, in addition to using the service for their own tools may act as 'agents' collecting instruments for the general public.

The sharpener usually has some sort of mobile work bench with a grinding wheel which may be powered by hand, using a bicycle mechanism or electric motor.

A hand-held tungsten carbide knife sharpener, with a finger guard, can be used for sharpening plain and serrated edges on pocket knives and multi-tools .
Video: Saw blade sharpening machine
Edge/Apex of a knife after sharpening and stropping. Although this edge is sharp enough to bite a thumbnail, cut paper smoothly, or shave arm hair, the microscope plainly shows an edge which reflects light back into the lens. A truly sharp edge is too thin to reflect significant light.
Sharpening tools
A two-man team sharpen a knife at high speed
sharpening of cutlass
A roadside knife grinder on rue Faidherbe (11e arrondissement) in Paris. He is one of the few knife grinders who still practise in France.
Sharpening tools
A cook for railroad workers sharpens a knife on a stone wheel, in the fields of Western Australia , 1927