This article gives lots of information about different types of sharpeners as well as explanations on how they can play a huge part in your Art techniques too.
The art of sharpening pencils. I went to the American Academy of Art…, by Julia Lundman
A Guide to Manual and Electric Pencil Sharpeners - Jackson's Art Blog
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Pencil Sharpener Black, Manual Pencil Sharpener with Stronger Helical Blade to Fast Sharpen for Kids, School, Classroom, Home, Artists, Ideal for No.2/Colored/Art Pencils : Office Products
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How To Draw a Pencil Sharpener - speed drawing ( by Artist Alamgir)
The art of sharpening pencils. I went to the American Academy of Art…, by Julia Lundman