The forging of a blade as a sequence of images (photos by Sina Kühne)
|Steel has to glow.||On the scrap, the blade is cut off at an angle or only notched.|| |
|In the forge vise, the steel can be removed by moving it back and forth (protects the hammer track).||Heat everything up nicely again.|| |
|The arrow shows the direction in which the metal must move through forging.||Now the blade is forged on the round mandrel by hammering only on one side of the future cutting edge. As a result, the metal stretches at this point and becomes longer, thinner and slowly bends towards the back of the blade.|| |
|Edge forging drives the cutting edge further towards the back of the blade||If the curvature is too great, you have to straighten up on the track.|| |
|And hammer again on the cutting edge until it is the right thickness and curvature.||With the help of the auxiliary device described below, the tang is notched ... || |
and further forged.
The whole blade is straightened with the smoothing hammer.
Still not lying flat. Again.
Well, it works.
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The forging a knife is described in detail by BerglAnd (2002) and is easy to understand even for beginners. Important isthe experience at which temperature range the steel burns and thus becomes unusable. To do this, one should slowly heat a file in an experiment until it starts to sparkle like a sparkler. The light yellow color that the steel has achieved should be well memorized. The lower temperature range must always be used for knife forging so that the structure remains fine-grained.
Blade: carbon steel (turning tool)
Handle: ebony, mammoth ivory, pao pink
Tools for forging the knife
The device shown is used to cleanly set the blade down. It is inserted into the square hole in the anvil track. The blade is pushed upright between the two irons. The hammer is then hit on the upper movable iron and the tang is set off on both sides of the blade. The idea is from Thomas Schmidt from Munich (www.messerforum.net).
The normal glow
The last step after forging the blade shape on the forge is the so-called normalizing of the blade. The blade is heated 2 to 3 times in the embers to around 700 ° C to 750 ° C and then cooled in the air (a few minutes). This achieves a favorable crystal structure, which is important for further heat treatment.
The soft glow
After forging, the blade is hard and brittle. The steel must be annealed for further processing and the blade grinding. Several methods of soft annealing for carbon steels are described in the literature. Schroen (1984) recommends heating 6 to 7 times until the steel turns red and then cooling it in hot sand (15 to 20 minutes). You can also let the finished forged blade cool down slowly in the charcoal. For powder metallurgical steels, however, special guidelines apply to temperature control. A curing oven is best suited for this. The blade is wrapped in a layer of newspaper and then carefully enclosed with hardening foil. This prevents the blade from decarburizing.
In order to protect the grinding belts, the hard scale must first be removed with the help of an acid treatment. 20% phosphoric acid is suitable for this. The tinder has peeled off after a short time. Regrinding the outer shape of the blade is quick and easy with a bench grinder. The blade edge is sharpened on the belt sander. To do this, the center of the cutting edge is first marked and then the blade is ground from both sides. The cutting stick is ground to a thickness of about 0.3-0.4 mm. It must be exactly in the middle of the blade.
The punch has a size of 4 mm and a hardness of 58 HRC. The fly symbol stands for courage and perseverance. Even the "ancient Egyptians" were convinced of these characteristics and awarded their bravest soldiers flying medals.