If you find that your sharpener is not working effectively it is possible that a loose lead has been caught inside the mechanism. If this is the case you should take the sharpener to pieces and check for any broken pieces of lead that may be preventing the sharpener from sharpening.
For many years I have tried many types of sharpener, never finding one I liked until now. This sharpener by Derwent is fantastic giving very long sharp points, making them ideal for fine detail and used on the side for shading. This sharpener has given new life to my graphite and Inktense pencils, Highly recommended product. Carl Holland (Stoke-On-Trent, United Kingdom) on 16 Mar 2014
Excellent product David Spencer (Bradford, United Kingdom) on 6 Jul 2013
It sharpened soft crayons without breaking the point.
On first using it too much wood was cut off so next time the crayon was retrieved before being fully back which rectified this. It was better than the battery type as more control was offered especially being cramped to the top. The point was sharp and thin which could be an advantage - or not - depending on the type of work and user. Keith Capon (Godalming, United Kingdom) on 26 Dec 2014