Fillet knife sharpening

A fillet knife is a specialized knife for preparing fillets of fish, meat or poultry. It is characterized by a long, narrow and flexible blade. Good sirloin knives can bend almost in a circle. That is, the main distinguishing feature is exactly flexibility. This knife should work superfine, cutting off the thinnest pieces of fish or meat, often less than a millimeter thick. The knife must also pass over the bones, the spine and tendons, to separate the skin from the meat, leaving a minimum layer of meat and subcutaneous tissue. In addition to removing the skin and separating the meat from the bones, a sirloin knife can be used to cut the product into thin slices (slices). That is why filleting knives are in demand among professional masters of European cuisine, and among cooks specializing in making sushi and other Japanese dishes. Often a sirloin fish knife has a serrated edge for tail and fins processing.

The length of the traditional “fillet” varies from 10 to 30 cm. Usually in serial industrial production, the sizes of such knives are 10, 15, 19 and 23 centimeters. The thickness of the blade varies from 0.5 to 1.5 mm. The width of the blade is from 1 to 3 centimeters. In terms of blade profile, a sirloin knife often has a straight edge, sometimes slightly bent upwards. Narrower in width, the knife is used most often to cut off the fillet, a wider blade separates the loin from the bones. It should be noted that a well-sharpened “fillet” should easily cope with cutting across the side (abdominal) bones of medium-sized fish. And at primary blunting it is quite capable of working due to its geometry without much effort.

The optimum angle that is considered the accepted standard for the cutting edge of a “fillet knife” is 23+/-2 degrees. Professional sirloin knife is sharpened usually under the hand of a particular professional. There is also the elasticity of the blade, and whether he is left-handed or right-handed, based on this some of the approaches can be wider or narrower, etc. Usually, factory knives made in-line are sharpened on a grinder rather coarsely and without a micro grip. And knives that are made or sharpened individually are recommended to be sharpened according to the method of sharpening safety razor blades, i.e. with three facets of micro-piping. For example, such a variant is possible: after skinning preliminary sharpening on abrasive grit from 800 to 1000 at an angle of 18 degrees, final sharpening on abrasive 3000 grit at an angle of 20 degrees, finishing with natural stone or blank with paste at 23 degrees. The direction and the combination of the ribs during finishing are also individual. The criterion of a good sharpening of a filleting knife can be a simple test, when only the skin is easily removed from a tomato and the pulp is not affected.

When talking about the difficulty of sharpening a fillet knife, the main factor to consider is its flexibility. It is extremely difficult to maintain the angle when the blade is thin and flexible. It is especially difficult to do it with a long blade. And if at manual sharpening this issue is solved by precise, extremely easy movements of the approach on the stone, then on sharpening machines with a rotary mechanism light movements alone will not be enough. It is necessary to securely fix the knife, preventing the blade from bending on the tip or handle side and preventing sagging in the central part. To solve this difficult task, the Profile K03 sharpener is equipped with so-called “fillet clamps”. These clamps reliably hold any blade shape, ensuring that the jaws are in contact with the planes of the knife edge and that the blade has open access to the blade for machining. The fillet clamps are based on three basic elements: the base, flat springs, and clamping jaws. Powerful jaws are connected to the base through flat flexible springs, which provide a universal fit and when the knife is inserted into the clamp, the springs change from a free state to a tense state, thus the rigidity of the clamp is significantly increased. Also, the fixing and adjusting screws in the clamp bundle, form a rigid geometric system and at the same time, allow a wide range of adjusting the clamp to any shape of the blade and ensure symmetry of installation.

For sharpening of fillet knives Technostudio “Profile” offers two variants of clamps:

1. Fillet full-milled clamps. They are designed for fixing knives with the thickness of the shank up to 3.5 mm. The shape of the outer surface is radially convex, which allows you to set the minimum sharpening angles of 7.2 degrees. The clamps are made of a single piece of aluminum, allowing to adjust the clamp to any shape of the blade and ensure symmetry of installation. The width of the clamps is selected in such a way as to allow up to 4 clamps to be mounted simultaneously on the frame and securely fix even the most flexible fillet knife. It is possible to move the clamps independently along the entire length of the frame. There is no need for calibration. It is possible to sharpen: kitchen knives, filleting knives, keychain knives, dangerous razors, knives with “scandi-slopes” and other narrow long knives. The recommended knife length for these clips is from 30 to 300 mm. The minimum recommended blade width is 10 mm. The width of the clamp jaws is 21mm each.

2. Single Sirloin Clamp -a special clamp for narrow sirloin knives, with a reduced sharpening angle. The thin jaws of the clamp are made of structural spring-spring steel, which provides sufficient clamping force. The clamp with a modified jaw configuration and with the use of special screws has a maximum minimum sharpening angle of 6.5 degrees per side. The minimum width of the knife that can be fixed by the clamp is 10 mm, the maximum thickness of the blade is 2.5 mm. The clamp fasteners are anodized by default. It is recommended to use this clamp for sharpening small fillet knives as well as small knives with descending bevels like Victorinox and other folding knives and multitools. The recommended knife length for this clamp is from 50 to 200 mm. The width of the jaws of the single fillet clamp is 32 mm.