The JBO Thread Plug Gauge is a precision Go/No-Go gauge crafted for metric fine threads, designed to verify threaded holes quickly and confidently. Built for right-hand threads and rated to 6H, it ensures that M21 x 1 holes accept the correct mating parts every time, making it ideal for machining shops, assembly lines, and maintenance teams alike.

Made from hardened steel for lasting performance, this gauge stands up to daily use in demanding environments. Use the Go end to confirm the hole accepts a properly sized thread, and switch to the No-Go end to verify the hole does not exceed the maximum limit. The result is fast, repeatable checks that support high-quality assemblies with minimal downtime.

• Go/No-Go verification for rapid checks: Quickly determine whether a threaded hole falls within the acceptable range, speeding setup and reducing rework.
• Metric fine thread accuracy: M21 x 1, 6H: Precisely ground to the M21 x 1 standard with 6H tolerance, ensuring consistent fits in precision assemblies.
• Hardened steel construction: Built to resist wear and maintain accuracy over many inspections, delivering reliable performance in busy workshop environments.

This gauge helps you streamline quality control and assembly workflows by providing fast, dependable checks that minimize guesswork and rejects. With its durable construction and precise threading, it supports consistent results, shorter inspection times, and smoother production cycles—making it a practical, long-lasting addition to any toolkit.