Thread Ring Gages - Unified Inch

Thread Check, Inc. offers a complete line of AGD - American Gage Design, unified adjustable thread ring gages. Thread ring gauges and set plug gages are manufactured per ANSI/ASME B1.2. Thread ring gages are manufactured to an X tolerance in 1A, 2A and 3A go members and 2A and 3A no go members. Unified Series thread ring gauges are available in UNC, UNF, UNEF, and specials. Metric thread ring gages are commonly manufactured to class 6g as well as other class sizes e, f, and h.

AGD adjustable style thread ring gauges can only be calibrated by means of a set plug. See proper instructions for calibrating thread ring gages.

Truncated thread setplug gages have a thread with both a truncated and a full form thread for both the go and the no go member. The full form section inspects and sets the correct clearance and forms at the major diameter of the thread ring gage. The truncated section controls pitch diameter. A thread ring gage should be set on the full form portion of the setplug - the back portion. The ring is then turned onto the truncated portion and should have the same drag and fit as when turned through the full form. A thread ring gauge which spins quickly through the truncated section or “shakes” usually indicates wear.

All Thread Check thread ring gauges are root relieved for longer life and more accurate gaging. The gages are manufactured with a root clearance in the major diameter which eliminates the possibility of interference from the full form section of the thread setting plug and major diameter of the part being gaged. This feature assures that the thread flanks are making proper contact. The no go thread ring gage is truncated on the thread crest and additional clearance is provided in the root so that this gage is checking pitch diameter only.

Thread Check manufactures many types of special gages including pre‐plates, multiple starts, special leads, acme threads, buttress threads, square threads, extra length thread gages, and custom gages to print. All thread ring gages are traceable to N.I.S.T.

Thread ring gauges are designed to be used for go/no go gaging. Thread ring gages are used for inspecting external screw threads of manufactured parts. With go/no go thread ring gauges, an inspector can quickly pass or fail parts without taking time consuming readings from a measuring instrument. Go thread ring gages are built with a minus tolerance on pitch diameter and major diameter. No go ring gages are built with a plus tolerance on pitch diameter and major diameter. The go gage is used to verify the high limit. The no go thread ring gage is used to verify the lower limit. Fixed limit gages such as thread ring gauges are made to match the maximum and minimum material condition of the part.

Adjustable thread ring gages have 3 radial slots and one is slotted all the way through which allows for the ring gages to be adjusted and set to a master setplug gage. The adjustment mechanism for the thread ring gage consists of a locking assembly, sleeve, and adjustment screw. With this design, the pitch diameter on thread ring gauges can be adjusted within a range of .002" on small rings up to .010” on larger thread ring gages. All adjustment screws are sealed by wax or hot glue after being set with a setplug gauge to eliminate the possibility of tampering.

Thread ring gauges should be cleaned frequently with air so that they are free of dirt, chips and sludge. All thread ring gages should be coated with a gage preservative. Thread ring gauges should be treated as precision gages and handled with care. Using thread ring gages to break through burrs will quickly wear and damage them. An inspector should never spin the ring gages onto the parts as this will create friction and increased wear on the gage. It is advisable to hold the ring gage firmly and turn the work piece into it. With larger thread ring gauges the reverse may be true.

A no go or lo thread ring gage inspects the no go or lo functional diameter limit of product external thread. The no go thread ring gage, when properly set to its respective calibrated thread setting-plug, represents the no go (Lo) functional diameter limit of the product external thread. No go (Lo) thread ring gauges must be set to the applicable truncated or Hi-Lo setting plugs.

No go 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 no go thread ring gauges 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 “no go (Lo) functional diameter is acceptable when the no 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 due to the gagemaker tolerances of setplugs and the subjective nature of setting adjustable style thread ring gages.

Thread Check’s expert sales engineers can assist you in selecting thread ring gages for your applications.

#0-80 UNF 2A Go Ring Gage - Thread Ring Gauges