a twisted stem helical internal abrading and finishing tool is formed from abrasive containing plastic strips having transverse offset slits along the lateral edges and a longitudinal middle unslit portion . the strips may be stacked with the longitudinal middle unslit portions aligned with the longitudinal axis of a cotter pin , one end of the stack being placed in the bight of the cotter pin . the cotter pin is twisted about its longitudinal axis to form a helical twisted stem from which the slit lateral side or edges extend forming rectangular abrasive fingers uniformly helically arranged . the end of the cotter pin opposite the bight may be inserted into the chuck of a drilling or turning machine to hold and rotate the tool about the axis of the stem .