A Thread ring GO gage checks the maximum minor diameter and the maximum pitch diameter size in a part, the NOGO checks for the part not to exceed the minimum pitch diameter size on a part. Basically there are three types of gages on the market: Solid Thread Rings, AGD Thread Rings and "Southern Style" Rings.

One of the premiere manufacturers of thread and ring gages is Glastonbury Southern Gage which was formed in 1995 when two of the largest and oldest gage companies, Glastonbury Gage and Southern Gage, were united under one owner. Glastonbury Gage was founded in 1964 in Glastonbury, CT by individuals who had trained at Pratt Whitney Machine. 

Southern Gage was founded in 1955 in Erin, TN as an outgrowth of the Woodward Company. It grew to be a full service gage manufacturer with emphasis on thread gaging. During the 1980's Southern Gage became known for its educational and training programs on thread form and gaging. In 1995, the owner of Glastonbury Gage purchased Southern Gage from ITW.

In March 1999, the GSG Erin operations occupied its new 42,000 square foot state of the art manufacturing facility. It includes 5,000 square feet of laboratory space, temperature and humidity control for the entire plant, CNC thread grinding equipment and a streamlined process work flow. So now that you know who GSG is, here's the major differences between ring gages:

Solid Thread Rings

Solid Thread Rings are the ISO standard and this is the gage pictured above.
Used to set the Zero Systems variable ITC units.

This is the solid ring show at the right. Over time these tend to wear out quicker than other styles.

AGD Thread Rings

AGD thread rings comply with ASME/ANSI B47.1 gage blank standard.
Sizes below 1/4 (M6) are counterbored to hold specific length. Sometimes these AGD rings can be difficult to use because of the "go" and the "no-go" gages look very similar and operators must verify that they indeed have the correct one in their hands.  If you look closely at the picture on the right you will see that this one is a "no-go" gage.  The AGD style gage is one of the most common styles in use in most shops because it's versatile and relatively inexpensive. We'll break down some more details about this gage below.

SOUTHERN STYLE RINGS

The "Southern style" sets round and stays round through all adjustments due to eccentric design and opposing pressures of the adjusting and locking mechanisms.

The Southern Style, on the left, features the unique Automatic Helix Adjustment. The Helix path of the thread along the line of adjustment remains true in alignment throughout the entire life of the gage.

The conventional AGD Style, shown to the right, presents a misalignment of the threads at the adjusting slot when reset.

The Southern Style sets round and stays round through all adjustments, due to the eccentric design and opposing pressures of the adjusting and locking mechanisms.

The AGD Style hinges at the two terminal holes and becomes more and more egg-shpaed as the ring is adjusted.

The Southern Style Adjusting Screw contacts the conical seat of the insert, maintaining a rigid setting and holding the two thread ends in perfect alignment even through rough handling.

The AGD Style sleeve assembly permits the gage faces to become mis-aligned at the adjusting slot.

All GSG Thread Ring Gages are manufactured to ASME/ANSI B1.2 or B1.16M. Each thread ring gage is made of oil hardened Tools Steel.

If you need some more information here's how you set and adjust Southern Style Thread Ring Gages

If you want to find out more about Thread gages and Specifications try searching for the following terms:

• H-28 Federal Specifications for Screw Threads
• B1.1 Unified Inch Screw Threads
• B1.2 Gages and Gaging for Unified Inch Screw Threads
• B1.13M Metric Screw Threads - Profile
• B1.16 American Gaging Practice for Metric Screw Threads
• B1.20.1 Pipe Thread, General Purpose (Inch)
• B1.20.3 Dryseal Pipe Threads - Inch
• B1.20.4 Dryseal Pipe Threads - Metric
• B1.20.5 Gaging for Dryseal Pipe Threads
• B4.4M Inspection of Workpieces
• B89.6.2 Temperature and Humidity Environment for Dimensional Measurement
• Y 14.6 Screw Thread Representation
• MIL-STD-120 Gage Inspection