The JBO Thread Plug Gauge is a precision tool designed for metric fine threads, ideal for engineers, buyers, tradespeople, hobbyists, and anyone who needs to verify threaded holes quickly and accurately. It provides a clear Go/No-Go check so you can confirm that holes will accept mating parts with the expected fit.

This gauge targets Left Hand - M21 x 1 threads with a 6H tolerance, and it’s crafted for durability. The hardened steel construction stands up to regular use, delivering reliable performance over many inspections.

• Go/No-Go Quick Verification: test both the lower and upper limits of the hole quickly, enabling fast pass/fail decisions and reducing inspection time.
• Left-Hand Metric Fine Thread Compatibility: precisely matched to M21 x 1 left-hand threads, ensuring accurate checks for LH components and preventing misfits.
• Hardened Steel for Durability: precision-ground, heat-treated body resists wear and maintains accuracy after repeated insertions.

By using this plug gauge, you streamline quality control, reduce rework, and ensure consistent thread engagement across assemblies. The Go/No-Go design gives reliable, quick feedback, while the hardened steel body resists wear in busy workshops. With its specific LH M21 x 1 6H specification, it covers a precise niche, making it a dependable addition to toolkits for fabrication, repair, and inspection tasks.