an apparatus for comminuting waste material such as waste plastic sheet material , into progressively smaller pieces until a desired size is reached that may be recycled . the apparatus has a set of slowly rotating , intermeshing scissor rolls for receiving the waste material and shearing the material into smaller pieces . a paddle wheel conveyor receives the smaller pieces from the scissor rolls and moves the smaller pieces over a screen with the undersized smaller pieces passing through the screen defining the desired reduced size . the oversized smaller pieces that do not pass through the screen are reprocessed back to the scissor rolls by the paddle wheel conveyor . a vacuum pump draws air through the apparatus and the screen to facilitate the separation on the screen and entrains the undersized pieces in an air stream to convey the pieces from the apparatus .