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.
love this little manual sharpener, sharpen to a long point which allows you to see more of the paper in fine detail work. The grip that holds the pencil is just a bit too tight, but probably require to form the superpoint. Uses helical blade which never dulls and no batteries need. Cam Lam (Burnaby, Canada) on 25 Jun 2013
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