A method of making a longitudinal reinforcing structure for a wind turbine blade, the method comprising: a. providing an elongate master strip of reinforcing material having substantially flat first and second surfaces, the distance between the first and second surfaces defining the thickness of the master strip; and b. dividing the master strip transversely to form a first strip and a shorter master strip, the respective strips being arranged end to end such that a trailing end of the first strip is located adjacent a new leading end of the master strip; characterised in that: the step of dividing the master strip comprises removing material from a dividing region extending through the entire thickness of the master strip by moving a grinding device such as a grinding drum through the thickness of the master strip from the first surface of the master strip towards the second surface of the master strip, wherein the dividing region is shaped such that a chamfer at the trailing end of the first strip is created and/or a chamfer at the new leading end of the master strip is created when the master strip is divided; the method further comprising moving the grinding device in a curved path relative to the master strip so as to form curved chamfers at the trailing end of the first strip and/or at the new leading end of the master strip. a. providing an elongate master strip of reinforcing material having substantially flat first and second surfaces, the distance between the first and second surfaces defining the thickness of the master strip; and b. dividing the master strip transversely to form a first strip and a shorter master strip, the respective strips being arranged end to end such that a trailing end of the first strip is located adjacent a new leading end of the master strip; characterised in that: the step of dividing the master strip comprises removing material from a dividing region extending through the entire thickness of the master strip by moving a grinding device such as a grinding drum through the thickness of the master strip from the first surface of the master strip towards the second surface of the master strip, wherein the dividing region is shaped such that a chamfer at the trailing end of the first strip is created and/or a chamfer at the new leading end of the master strip is created when the master strip is divided; the method further comprising moving the grinding device in a curved path relative to the master strip so as to form curved chamfers at the trailing end of the first strip and/or at the new leading end of the master strip. the step of dividing the master strip comprises removing material from a dividing region extending through the entire thickness of the master strip by moving a grinding device such as a grinding drum through the thickness of the master strip from the first surface of the master strip towards the second surface of the master strip, wherein the dividing region is shaped such that a chamfer at the trailing end of the first strip is created and/or a chamfer at the new leading end of the master strip is created when the master strip is divided; the method further comprising moving the grinding device in a curved path relative to the master strip so as to form curved chamfers at the trailing end of the first strip and/or at the new leading end of the master strip.