Handy metal sharpeners from Staedtler
For standard-sized blacklead pencils up to 8.2 mm with a sharpening angle of 23 degrees for clear and accurate lines
For thick blacklead and coloured pencils up to 10.2 mm with a sharpening angle of 30 degrees for broad, soft lines
A quality metal sharpener from Staedtler, designed for their pencils but a universal fit for most other makes.