Employing a cutting fluid which comprises a base oil having characteristics adapting it for use in the operation of electrical discharge machinery and which is based on a mineral oil, a synthetic oil or a mixture thereof, and an additive component effective to increase the speed of operation of said machinery and which is at least one alkylbenzene in an amount of from 10 to 40 percent by weight of the total cutting fluid, said base oil having a kinematic viscosity of 1.4 to 3.5 centistokes at 40° C., and said alkylbenzene having a kinematic viscosity of 5 to 16 centistokes at 40° C.