PURPOSE: To allow internal tensile stress to remain in the specific section of a circular saw so that clattering and oscillating of the circular saw during cutting are effectively prevented by attaching rings to the sections of the prescribed radial circle on both side faces of the circular saw and subjecting the entire part to quick heating and quick cooling.
CONSTITUTION: Respectively circular residual tensile stress parts 1b are held on both side faces 1a of the circular saw 1. The radius of the circular saw is designated as R and the radius of the residual tensile stress 1b as (r), then (r) is so set as to satisfy 0.65R≤r≤0.8R. Respectively the same metallic rings 2 are mounted by means of a bolt and nut 3 to both side faces 1a of the circular saw 1 in order to form said residual tensile stress 1b. The rings 2 having the larger heat capacity are more preferable and therefore, the thickness thereof is made substantially large. The diameter and width thereof are made to coincide with the diameter and width of the parts 1b. The circular saw 1 with such rings is carried into a heating furnace 4 and is uniformly heated overall to the temp. above the tempering temp. of the circular saw 1 and below the A3 transformation point thereof; thereafter, the circular saw is taken out of the furnace 4 and is quickly cooled by immersing the same into cooling water or cooling oil in a cooling tank 5.
ISODA SHIGEO
KAKIHARA KUNIO
YAMASATO KAZUO
KISHIMOTO KOICHI
HINO MASAYASU
