Abstract: An electrical discharge machining oil composition of the invention includes an organic acid metal salt and a base oil, in which the organic acid metal salt is an organic acid salt of a metal having an electronegativity on Pauling scale of 2 or less, and the present composition has a volume resistivity at 80 degrees C. of 2×10?5 T?·m or more and a kinematic viscosity at 40 degrees C. in a range from 0.5 mm2/s to 10 mm2/s.

Abstract: An electrical discharge machining oil composition of the invention includes an organic acid metal salt and a base oil, in which the organic acid metal salt is an organic acid salt of a metal having an electronegativity on Pauling scale of 2 or less, and the present composition has a volume resistivity at 80 degrees C. of 2×10?5 T?·m or more and a kinematic viscosity at 40 degrees C. in a range from 0.5 mm2/s to 10 mm2/s.

Abstract: An electric discharge machine for machining a workpiece (2a) made of insulating material or other materials comprises: a first comparison member (17) for comparing voltage (V) between the electrodes of the electrode (1) and the workpiece (2a) with the first reference voltage (V1) which is set at a value close to electric power source voltage (V0) not higher than electric power source voltage (V0); a second comparison member (18) for comparing voltage (V) between the electrodes with the second reference voltage (V2) which is set at a value lower than the first reference voltage (V1); and a control member (19) for setting a short electric discharge pulse width (TP1) in the case where voltage (V) between the electrodes is lower than the second reference voltage (V2) according to the result of comparison conducted by the second comparison member (18) at a point of time when a predetermined period of time (T0) has passed from the time when voltage (V) between the electrodes becomes lower than the first reference v

Abstract: An electric discharge machine for machining a workpiece (2a) made of insulating material or other materials comprises: a first comparison member (17) for comparing voltage (V) between the electrodes of the electrode (1) and the workpiece (2a) with the first reference voltage (V1) which is set at a value close to electric power source voltage (V0) not higher than electric power source voltage (V0); a second comparison member (18) for comparing voltage (V) between the electrodes with the second reference voltage (V2) which is set at a value lower than the first reference voltage (V1); and a control member (19) for setting a short electric discharge pulse width (TP1) in the case where voltage (V) between the electrodes is lower than the second reference voltage (V2) according to the result of comparison conducted by the second comparison member (18) at a point of time when a predetermined period of time (T0) has passed from the time when voltage (V) between the electrodes becomes lower than the first reference v

Abstract: An insulating material is electric discharge machined with high dimensional accuracy at a high speed, by closely adhering mesh-shaped electroconductive material 5 onto the surface of an insulating material 1 so as to form an electroconductive layer 6 at the initial stage of electric discharge. In the advancement of electric discharge, fresh electroconductive layers 9, 10 are continuously formed at the bottom and the side surface of a hole 8, so that the electric discharge machining is continued even after the hole 8 becomes deeper. A porous preformed body composed of fine metal wires or a complex body containing needle metal may be used instead of the mesh-shaped electroconductive material 1. Thus, electric discharge machining is performed at a high speed, and a machined surface excellent in flatness can be obtained with high dimensional accuracy.