UL 498:2019 Figure SC25.1 Oversize Grounding Probe

The GNGPL-SB0705-SC25.1 is a specialized gauge—specifically the “Oversized Grounding Pin” (Part No. SB0705) defined in UL498:2019 Figure SC25.1—designed for testing American-standard plugs and receptacles. Precision-machined from hardened steel, it features a spherical tip and an 8-micro-inch surface finish, serving to verify the maximum acceptance dimensions of the grounding contact opening. If this pin fails to seat fully, test pins of the same configuration but larger diameters can be custom-ordered (starting from a minimum reference diameter of 0.190 inch / 4.83 mm), all in strict compliance with the specifications in UL498:2019 Appendix SC25.1.

Specifications:
• Standard Reference: UL 498:2019 Figure SC25.1, SB0705
• Material: Hardened steel
• Nominal shank diameter: 0.5 inch (13 mm)
• Tip diameter: 0.203–0.204 inch (5.16–5.18 mm)
• Effective working length: 0.840–0.843 inch (21.34–21.41 mm)
• Surface finish: 8 microinches (200 nm), ground in the specified direction
• Handle length: Not specified
• Supplementary provision: If this pin fails to seat fully, a test pin with the same profile but a larger diameter may be used (minimum reference diameter: 0.190 inch / 4.83 mm).

Test Procedure:
• Securely mount the receptacle under test, keeping the grounding slot facing vertically upward;
• Allow the oversized grounding pin to lower into the grounding slot under its own weight, without applying additional external force;
• Check if the gauge seats fully to determine compliance with the maximum limit dimensions of the grounding slot;
• If the pin fails to seat fully, re-test using an alternative pin of the same configuration but larger diameter (minimum reference diameter: 0.190 inch);
• Evaluate the dimensional margin and mating performance of the grounding structure against relevant UL 498 clauses;
• Remove the gauge after testing, clean and apply anti-rust treatment, and perform periodic metrological calibration.

Industry Applications:
• UL safety type testing for plugs and receptacles
• Verification of maximum envelope dimensions for grounding slots
• Production line finished product inspection and incoming material dimensional control
• Use by ILAC-accredited third-party testing laboratories and electrical manufacturing quality control departments

UL 498:2019 Figure SC25.1