The JBO Thread Plug Gauge is a precision tool for verifying No. 4 x 40 (4-40) left-hand UNC threads. Designed for inspectors, machinists, and technicians across manufacturing, automotive, and aerospace environments, it helps ensure threaded holes and mating parts conform to Unified thread standards with speed and accuracy.

Featuring a 2B tolerance grade and a robust go/no-go design, this gauge delivers fast pass/fail checks, reduces inspection downtime, and supports consistently reliable assemblies in busy workshop settings.

• Go/No-Go quick conformance checks: Quickly determine whether the thread is within specification by testing against the go and no-go limits, enabling faster acceptance/rejection decisions and less rework.
• 2B tolerance for reliable results: The 2B tolerance grade ensures repeatable measurements across parts, reducing variability and helping quality teams meet tight standards.
• Durable, ergonomic construction: Knurled handle and sturdy ends withstand daily shop use, providing a secure grip and consistent readings even in demanding environments.

Using the JBO Thread Plug Gauge streamlines your thread inspection workflow. It minimizes guesswork, speeds up quality checks, and helps prevent mismatches in critical assemblies. With clear go/no-go feedback and durable design, you can rely on accurate evaluations every shift, improving first-pass yields and reducing downtime across production lines.