Techniques are described for controlling widths of nanofiber sheets drawn from a nanofiber forest. Nanofiber sheet width can be controlled by dividing or sectioning the nanofiber sheet in its as-drawn state into sub-sheets as the sheet is being drawn. A width of a sub-sheet can be controlled or selected so as to contain regions of uniform nanofiber density within a sub-sheet (thereby improving nanofiber yarn consistency) or to isolate an inhomogeneity (whether a discontinuity is the sheet (e.g., a tear) or a variation in density) within a sub-sheet. Techniques for dividing a nanofiber sheet into sub-sheets includes mechanical, corona, and electrical arc techniques.