The JBO Thread Plug Gauge – UNJF Go-No/Go – Left Hand – 3B – 1/4 x 28 is a precision inspection tool engineered to verify left-hand UNJF threaded holes and components. Sized for 1/4-28 threads with a 3B tolerance, it helps quality teams, machinists, and inspectors quickly confirm whether a hole will accept the mating thread without guesswork.

• Go/No-Go design for fast acceptance testing: enables immediate pass/fail decisions on threaded holes, speeding up inspections and reducing downtime in production lines.
• Specialized for left-hand UNJF threads: precisely calibrated for left-handed 1/4-28 UNJF threads to prevent mismatches and ensure reliable fit and function.
• Rugged, precision-graded construction: a durable metal body with a secure grip and robust thread ends supports repeated use in demanding shop environments while delivering consistent measurements.

This gauge helps streamline quality control by delivering clear, repeatable results that support accurate assembly and long-term reliability. By providing quick verification of thread conformity, it reduces rework, protects part interoperability, and keeps your workflow moving smoothly from inspection to final assembly.