PURPOSE: To machine each edge of parallel grooves into a linear edge, by cutting these parallel grooves with a disc saw after grooving a cutter inserting groove on a metal plate in use for altering an interval of letters on a solenoid printer or the like, while embedding a metallic stuffing plate into the cutter inserting groove.

CONSTITUTION: Two cutter inserting grooves 2 are parallelly grooved in a steel plate 1. Each of parallel grooves 3 is made up of the following formation that it is 0.4W0.8mm in width, 0.4mm in depth and 0.8W1.6mm in pitch, and their numbers are set down to a range of 520W350 pieces or so, and as for a cutting tool (disc saw) (a), a disc saw of 24mm in a radius is used, thus each parallel groove 3 is formed up by means of milling operation. Unless this cutting tool (disc saw) (a) comes off both longitudinal ends of each parallel groove 3 in its shaft center and yet gets situated outward away, however little, from an inner edge 2a of the cutter inserting groove 2, the cutter (a) bumps against its outer edge groove 2b, damaging it. After cutting these parallel grooves 3, each metallic stuffing plate 4 being produced in conformity with form in each cutter inserting groove 2 is forcibly fitted in these inserting grooves 2 and secured thereat, then each of these plates 4 is made to produce a slight projection and finished with a grinder or sandpaper, etc., to be flush with the steel plate 1.