Complex sentence: Carpenter pencils are typically manually sharpened with a knife, because their shape makes them unable to fit into a mechanical pencil sharpener, although recently a fixed-blade pencil sharpener with a rotatable collar has become available.
Split into simpler sentences: Carpenter pencils are typically manually sharpened with a knife, because their shape makes them unable to fit into a mechanical pencil sharpener. Recently a fixed-blade pencil sharpener with a rotatable collar has become available.