Knife Service Terms

Bevel – The portion of a blade that has been shaped with grinding equipment or flat stones. Knives often have multiple bevels. At the very front of the bevel (the bottom of the blade) is the edge.

Blade – A blade is the entire flat portion of a knife that has an edge and is used for cutting.

Buffing – Buffing is an abrasive process that removes a limited amount of material from a blade. Buffing wheels are made in many different shapes, diameters, and material. A composite buffing wheel is the same grit throughout, as opposed to cotton buffing wheels that are coated with ‘rouge’ or buffing compound. Compound can be purchased in both coarse and fine grits, and when applied to a cotton wheel, the compound itself is what establishes the level of abrasiveness. Buffing is performed after edging to ‘buff out’ some of the deeper grinding marks and scratches that occur while grinding. De-burring is also achieved with a buffer. Cosmetically, the buffer can be used to achieve extremely high levels of finish. Most knife services exclude buffing from their process, but the result is a less finished blade that has more drag.

Diamond Sharpener – Much the same shape as a honing steel, diamond sharpeners are coated with diamond dust, and are aggressive enough to remove a substantial amount of material from a blade. When a knife has a good edge, it is best to avoid using a diamond sharpener because at the wrong angle, a diamond sharpener can remove or damage the existing edge. With the PostKnife subscription, customers receive knives every two weeks that have a new factory edge, therefore, the potential damage that can be done to a PostKnife edge with a diamond sharpener is not worth the risk.

Edge – Usually located at the bottom of a knife blade, an edge is shaped for cutting, and is made up of steel fibers. As those steel fibers bend and break off, the edge becomes dull and completely deteriorates. A chef’s knife will have a very fine edge made up of longer, fine steel fibers. Alternatively, the edge of a cleaver is very short because the shape of the blade does most of the work.

Edging – Shaping the bevel that makes up the actual cutting edge of a knife is called edging. There are many different methods for edging knives. At PostKnife, flat grinding and edging are interchangeable terms because flat grinding is the method we use for edging.

Flat Grinding – Flat grinding is done on a water-cooled grindstone to shape a flat ground edge. Flat grinding can be performed free hand or with the assistance of a chuck at many different angles. 15 to 30 degrees is the most common angle range used for a flat grind. The stone used for flat grinding is very coarse, and if operated properly can cut a precision edge into a blade. A flat grind can be adequate for almost any blade, but the angle will vary depending on the thickness of a blade and what that blade is used for. Chef’s knives, boning knives, santoku’s, slicers, and parer knives; flat grinding can be used to shape an edge on any of these knives. Though flat grinding is the traditional method for knife rental and exchange services to use, for simplicity in training and therefore consistency, most sharpening companies have shifted to edging by edging machine

Flat Stone or Whet Stone - Flat stones are abrasive stones which come in a wide range of grit, that are used for both maintaining and shaping the edge of a knife. In more mechanized grinding processes, flat stones can be used during the finishing stages. Knives can be sharpened start to finish with flat stones.

Front Edge – The sharp and finely shaped part of a knife that comes into contact with and physically cuts, is the front edge.

Grit – In a grinding shop grit has at least three different meanings. The first refers to the sand like material that results in the degradation and waring away of a grindstone. Secondly, grit is often used to refer to the level of coarseness that any abrasive material has. In the grinding shop, the grindstones, buffing wheels and compounds, and the honing stones are made with different levels of grit. Thirdly, a manly or womanly quality of character displayed by a person in the grinding shop can be referred to as grit.

Hollow Grinding - A thinning process used by nearly all professional knife rental services that simultaneously removes steel from both sides of a blade. The motion of inserting a blade and drawing it back out between two circular grind stones that are very close together (or touching slightly), while both grind stones are rotating in the same direction, rapidly thins a blade. The hollow grinding stones that we use at PostKnife are 40 grit; this is very aggressive. The resulting shape is a concave on both sides of the knife.

Honing – The last step in shaping an edge is honing. If there is a burr on the front edge of a knife, honing will be used to remove it. Honing will remove a small amount of material from a blade, but most important is the removal of the wire edge, revealing a finished front edge.

Honing Steel - There are a wide range of honing steels that are referred to as honing rods or sharpening steels. The type that maintain an edge are made of steel, while ceramic steels remove material and can be used to shape an edge. Most people think of sharpening knives as using a honing steel to realign the edge.

Knife Exchange Service – Companies that provide rental knives to their customers and then deliver sharp replacement knives on a routine basis. Most knife exchange services, also referred to as ‘knife rental services’ or just ‘knife services’, have common roots to the northern Italian province of Trentino.

Knife Rack – A holder of knives that is commonly installed to a wall. Most knife racks come in the form of a narrow strip with a magnetized surface. Another common style is a narrow rectangular box, made of stainless steel or plastic, that has slots allowing for knives to be individually inserted. A knife rack ideally establishes a clean and safe place for knives to be stored in a kitchen. When used in conjunction with a knife service, a knife rack makes the knife exchange process much easier by having a defined location to store knives.

Knife Rental Service – see ‘Knife Exchange Service’

Knife Service – see ‘Knife Exchange Service’

Knife Sharpening Service by Mail – a company that provides all of the materials necessary to easily ship your personal knives in for sharpening, professionally sharpens your knives for you, and then returns the knives back to you by mail or some other delivery service.

Roll Grind – A roll grind refers to shape that is used primarily on thick blades used for splitting bones. The profile of this type of grind is convex and can be shaped on a water-cooled grindstone. A roll grind is appropriate for cleavers and a range of splitters.

Sharpen – The most basic definition is to make something sharp or sharper. Therefore the term ‘sharpen’ is quite broad and should be separated into at least two categories; the first, ‘shaping a new edge’, and the second, ‘maintaining an existing edge’. Both are commonly referred to as sharpening, but they are distinct. Shaping a new edge is an abrasive process that involves removing material from a blade in a precise way. Maintaining an existing edge is realigning and straightening an edge that is out of line or folded to one side or the other.

Temper – The quality of hardness and elasticity in steel that is achieved through the heat treatment process.

Wire Edge – The wire edge, also referred to as a ‘burr’, is what remains connected to the front edge of a blade after an edge has been shaped. When shaping an edge the bevel is cut into the blade, and as material is removed at the appropriate angle the bevel eventually reaches the front edge. Once the bevel reaches the front edge, a wire edge begins to form. The wire edge is waste, and must be removed to expose the front edge.