Logset provide us with technical advice on how to correctly sharpen delimbing knives.
When the delimbing knives of a harvesting head are sharp, they easily cut the branches off and the quality of the logs increases. Measuring the volumes of the logs through length and diameter readings are also more accurate when the branches are cut flush with the stem. At the same time, the effectiveness of the harvester is increased and the fuel consumption is reduced.
The delimbing knives should be sharpened on a regular basis. When the knives are sharp, the tree moves easily through the harvesting head and the branches are cut off flush without being ripped off. However, the sharpening of the delimbing knives often provokes discussion. How and when should the knives be sharpened? There are several different ways to go about the sharpening of the delimbing knives. Also, different tree species should be considered. The front knife, the delimbing knives and the rear knives of the harvesting head should all be sharpened.
Logset explains that one should start by analysing whether the knives are really dull or just in need of a touch up. The delimbing knives should be as sharp as a kitchen knife. Logset suggests testing the sharpness with your own nail. Knives should be sharpened with an angle grinder so that the abrasive paper disc spins away from the knife. Move forward at a suitable pace so that the knife doesn’t become too warm. If the knife is heated, the hardness of the material will suffer and may cause cracks in the knife. When you’re done, you can measure the edge of the knife with an adjustable angle measuring gauge. The inside edge should be straight and the outside edge should be about 30 to 35 degrees. If the knife is sharpened correctly, the inside edge is straight and the outside edge is about 30 to 35 degrees, depending on which tree species the harvesting head is operating in. Source