JBO Thread Plug Gauge - UNC Go-No/Go - Left Hand - 2B - No. 4 x 40 FHH Built in high-speed steel (M2)

Built in high-speed steel (M2)

repeatable fits in mechanical assemblies

providing flexibility for a variety of machining scenarios

Designed for a broad audience—from engineers and buyers to machinists and hobbyists—it helps you quickly confirm that threaded parts conform to required specifications

JBO Thread Plug Gauge - UNC Go-No/Go - Left Hand - 2B - No. 4 x 40 FHH Built in high-speed steel (M2)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