Why Osborn Products?


  • ISO 9001:2008 Certified
  • AS9100 Rev C Certified
  • Aerospace Quality Gages
  • Precision CNC Machining & Grinding
  • Made in USA
  • Established in 1956

Not Go Gaging Per ANSI/ASME B1.2-1983 An American National Standard


Not Go ( Lo ) Thread Ring Gage

A Not Go or Lo thread ring gage inspects the Not Go or Lo functional diameter limit of product external thread. The Not Go thread ring gage, when properly set to its respective calibrated thread setting-plug, represents the Not Go (Lo) functional diameter limit of the product external thread. Not Go (Lo) thread ring gages must be set to the applicable truncated or Hi-Lo setting plugs.

Not Go (Lo) thread ring gages when applied to the product external thread may engage only the end threads (which may not be representative of the complete product thread).

Starting threads on Not Go (Lo) thread ring gages are subject to greater wear than the remaining threads. Such wear in combination with the incomplete threads at the end of the product thread may permit further entry in the gage.

As stated in ANSI/ASME B1.2-1983, the "Not Go (Lo) functional diameter is acceptable when the Not Go (Lo) thread ring gage applied to the product external thread does not pass over the thread more than three complete turns." The gage should not be forced. Special consideration such as exceptionally thin or ductile material, small number of threads, etc., may require modification of accepting up to 3 turns of the gage. It is highly recommended that a manufacturer not allow a maximum of 3 turns during thread fabrication as every thread ring gage is set slightly different to due the gage maker tolerances of setplugs and the subjective nature of setting adjustable style thread ring gages.

Not Go ( HI ) Thread Plug Gage

The Not Go (HI) thread plug gage inspects the Not Go (HI) functional diameter limit of product internal threads. The Not Go (HI) thread plug gage represents the Not Go (HI) functional diameter limit of the product internal thread.

Thread plug gages when applied to the product internal thread may engage only the end threads (which may not be representative of the complete thread). Entering threads on product are incomplete and permit gages to start. Starting threads on Not Go (HI) plugs are subject to greater wear than the remaining threads. As Stated in ANSI/ASME B1.2-1983, the “Not Go (Hi) functional diameter is acceptable when the Not Go (Hi) thread plug gage applied to the product internal thread does not pass over the thread more than three complete turns.” The gage should not be forced. Special consideration such as exceptionally thin or ductile material, small number of threads, etc., may require modification of accepting up to 3 turns of the gage. It is highly recommended that a manufacturer not allow a maximum of 3 turns during thread fabrication as every thread plug gage may gauge differently due the actual size and gage maker tolerances allowed.