PURPOSE: To prevent warping of core by fitting the tubular section of an assembling jig to the outer circumference of an insulated core placed in an insulator while extending over a conductor lead-out section and the tip of a rubber mold stress cone thereby pressing the stress cone.

CONSTITUTION: A cable termination 1 is stripped in step and a conductor lead- out rod 3 is compression adhered to a conductor 2, then a cable protective metal 4, a compression unit 5 and a rubber mold stress cone 6 are inserted sequentially from the lead-out rod 3 side of the cable termination 1. Then the cable termination 1 is cowered by an epoxy seat 7 and an insulator 8. Thereafter, a jig 19 comprising a tubular section 20 and a flange section 21 is inserted from the tip of the insulator 8 so that the tubular section 20 covers from the lead-out rod 3 to the stress cone 6. The stress cone is pressed by means of the compression unit 5 and positioned, then the jig 19 is removed. Compound is injected into the insulator a sealed by a tape 14 and the lead-out rod 3 is secured to the end section of the insulator 8 through a metal(not shown). By such arrangement, the insulated core is protected from warping resulting in the improvement of electrical characteristic.