Osg 1500300200 Thread Limit Gage 4-40 Unjc 3B Go No-go

Product Description

The OSG 1500300200 is a double-end Go/No-Go thread limit gage designed to verify internal thread conformance to the 4-40 UNJC 3B classification. Machined from high-speed steel with a bright, uncoated finish, this gage checks both the minimum and maximum material condition of a tapped hole in a single tool. The Go end confirms the thread will accept a mating fastener, while the No-Go end confirms the thread has not been cut oversize. It ships calibrated and is ready for immediate use on the shop floor or in a quality inspection station.

This gage is suited for production inspection, incoming inspection, and field verification wherever 4-40 UNC or UNJC threaded holes are produced or assembled. Typical applications include precision machined components, aerospace hardware, and electronic assemblies where 4-40 threads are common. The double-end design keeps the Go and No-Go members on a single handle, reducing bench clutter and the risk of mixing up individual plug members during high-volume checking operations.

Key Features

• Go and No-Go members on a single double-end handle for efficient thread verification
• Calibrated at the factory — ready to use out of the box without additional setup
• High-speed steel construction provides wear resistance for extended service life
• Bright, uncoated finish allows easy visual inspection of the gage surface for wear or damage
• Conforms to 3B classification tolerance limits for 4-40 UNJC internal threads

Compatibility

Designed for inspection of internal threads conforming to the 4-40 UN(J)C 3B standard. Suitable for use wherever 4-40 UNC or UNJC tapped holes must be verified to Class 3B tolerance limits.

Installation Notes

Thread limit gages are inspection tools, not cutting tools — never force the gage into a tapped hole. The Go member should pass through the full thread length under hand pressure only; if resistance is felt, the thread may be undersize or contain chips and should be re-examined. The No-Go member should not enter more than two turns; entering beyond that indicates the thread is oversize. Store the gage in its protective case when not in use to prevent nicks or corrosion that would affect calibration accuracy.