The primary grind is where a

knife A knife (: knives; from Old Norse 'knife, dirk') is a tool or weapon with a cutting edge or blade, usually attached to a handle or hilt. One of the earliest tools used by humanity, knives appeared at least Stone Age, 2.5 million years ago, as e ...

first begins to narrow into a cutting edge from the thickness of the main stock of the

blade A blade is the Sharpness (cutting), sharp, cutting portion of a tool, weapon, or machine, specifically designed to puncture, chop, slice, or scrape surfaces or materials. Blades are typically made from materials that are harder than those they a ...

. The cross-sectional shape of the blade of a knife or

sword A sword is an edged and bladed weapons, edged, bladed weapon intended for manual cutting or thrusting. Its blade, longer than a knife or dagger, is attached to a hilt and can be straight or curved. A thrusting sword tends to have a straighter ...

is made up of different planes, or grinds. The sharp, cutting edge of the blade is often further ground at a secondary, or 'edge', bevel. This allows the blade to have more functions than otherwise possible with a strictly wedge or chisel shape. The Swiss Army Knife is an example of a knife with a primary bevel and an edge bevel. By contrast, a blade composed of a single flat grind from stock thickness to the cutting edge is known as a 'full flat ground' blade. The cutting properties of a blade are determined by the type of metal, the hardness of the blade, and the grinding pattern (e.g. convex, concave, teardrop).

References

Knives {{metalworking-stub