Technically, you're not supposed to splice extension cords. Even if you solder the wires, wrap each wire with electrical tape and encase the whole splice in heat shrinkable tubing, it still won't have the abrasion resistance of a new cord. Plus, it's not permissible under the National Electrical Code.
Also know, what does it mean to splice a wire?
Electrical splice, the joining of wires in electrical wiring. Optical splice, the joining of optical fibers: Fusion splicing, a permanent splice between two fibers. Mechanical splice, a temporary splice between two fibers.
Can you splice stranded and solid wire?
If you hold the ends of solid and stranded wire even with each other while you screw on the wire nut connector, the stranded wire will often wrap loosely around the solid wires, resulting in a loose connection. The problem is easy to prevent by extending the ends of all stranded wires about 1/8 in.
Can you splice wires with electrical tape?
Connecting two wires can be done with a wire stripper and electrical tape, but to make a proper connection you should solder them together, or at least use wire nuts. Wire nuts are screwed clockwise over the end of a pigtail splice or twist and fold as shown in the video above.