The JBO Plug Gauge for UNC (STI) is a precision inspection tool built to verify UNC screw-thread inserts (STIs). Part of the Helicoil gauge family, it’s ideal for engineers, buyers, technicians, and inspectors who need fast, reliable checks on No. 4 x 40 inserts to ensure proper seating and performance in assemblies.

Manufactured and assessed to ANSI/ASME UNC standards, this plug gauge provides accurate pitch-diameter checks for UNC STI inserts. It features a right-hand orientation and DAkkS-calibrated accuracy, delivering traceable measurements you can trust for quality control across automotive, aerospace, and general manufacturing environments.

• DAkkS-calibrated, traceable accuracy: The gauge is calibrated to DAkkS standards, ensuring measurements you can rely on for audits, certifications, and consistent production quality.
• Designed for UNC (STI) wire inserts: Specifically built to verify pitch diameter and UNC STI specifications, helping you confirm proper fit of No. 4 x 40 inserts.
• Right-hand orientation with a durable, knurled body: The ergonomic, easy-to-grip design supports repeatable readings in busy work zones and enhances reliability over long-term use.

Using the JBO UNC plug gauge streamlines quality checks, ensures consistent insert fit, and delivers dependable readings across shifts. With DAkkS calibration, ANSI/ASME accuracy, and a rugged construction, this gauge supports confident, efficient inspections for manufacturing, automotive, and aerospace applications.