Spark plug with low erosion electrode tip

In a spark plug comprising:

• an insulating core having an axial bore therethrough, a center electrode mounted in said bore, an outer grounding shell surrounding said insulating core and a ground electrode electrically connected to said outer shell, an improvement, including:
• a thermal energy conducting sheath surrounding said center electrode within said bore;
• and,
• an iridium disc in intimate contact with bore said sheath and said center electrode, oppositely positioned across an air gap from said ground electrode, wherein said iridium disc has a frusto-conical aperture with a smaller diameter closest to said center electrode and said center electrode has an enlarged end that extends into said aperture and is larger than said smaller diameter of said aperture to provide an electrical conduction path between said disc and said center electrode.