Long Cone Sharpener – Þýsk Gæðavara –
Highest quality and precision! Sharpeners have been KUM’s core competence since 1919.
They are known worldwide for their high quality and precision.
The most important component is the knife. If a knife does not work cleanly and reliably,that is, sharpens the pen, then the entire sharpener is worthless.
Our knives are manufactured with a measuring tolerance of 5/100 mm. The hardening of these knives is equally important. We harden the steel with 64 HRC. For comparison and understanding: top knives for use in the kitchen have a maximum of 53 HRC. These sub-processes are the most complicated when manufacturing the product. This hardness is necessary because pencil leads contain clay, which is a type of rock. Metal is usually ground with stone, but the sharpener does the opposite!
Carbon steel rusts relatively easily, therefore every KUM knife is protected by three careful processes: 1) polishing, 2) ultrasonic cleaning, 3) coating with oil. This protection lasts for many years – except in a tropical climate with high relative humidity with salt water, where tiny rust spots can appear after 6 months. A knife made of stainless steel cannot be used with sharpeners because it cannot be sharpened sufficiently. Example kitchen knife: You always have cutting „teeth“. However, rust does not affect the performance of a sharpener in continuous use, because the sharpening process cleans the knife constantly.
Dynamic torsion action
We are the only manufacturer in the world to equip our sharpeners with a curved knife. Due to the curved knife, the knife edges are under constant tension and are not raised by the pressure when sharpening. This means that the pen tip cannot “bounce” or “tear”. Furthermore, pressure against the screw prevents it from loosening or loosening.