The quality of the sharpener, especially the blade, is crucial for optimum sharpening of wood-cased pencils. Pencils can be sharpened particularly slim and thin due to their robust and hard leads. Coloured pencils are sharpened shorter and blunter due to their softer lead. To ensure optimum sharpening, we recommend replacing the sharpener from time to time, as the sharpener blade becomes blunt over time, leading to increased tip breakage.