Below is a basic use of a GO / NOGO gauge for straight threads, such as Unified National (UN), Metric threads, Acme / Stub Acme and other straight thread connections:
Using thread plug and ring gauges is a simple effective and economical way to pass or fail a threaded connection. This type of inspection is also called limit gauging as we don’t determine dimensions of the part thread but can confidently say it is within the upper and lower limit of the specification.
Essentially the GO gauge is designed to enter the part and the NOGO gauge is not. When the go plug gauge enters the female connection or box connection it is proven to be NOT too small. When the NOGO plug gauge fails to enter the part this ensure that female connection is NOT too large. Therefore, it is safe to determine that the female connection is in tolerance and between the known sizing of the GO plug member and the NOGO plug member. The inverse is true for ring gauges. When GO ring enter the pin or male threaded connection that ensures that the sizing of the pin is not too Big. When the NOGO ring doesn’t enter the pin that means that the pin is NOT too small.
Every time a fastener is used to form a joint between two parts, torque control is a key element of that formula. Ensuring a well-tightened fastener is installed properly to the pre-defined torque specification will determine the success or failure of a product. Torque testing is key to identifying and reducing fastening failures.
A lack of monitoring and measuring torque is a lack of quality control. Insufficient torque can cause a screw or bolt to loosen from vibrations. Excessive torque can cause fasteners to overstretch and break. After a torque specification is determined for a joint, it is a good practice to perform periodic audits to verify proper torque is being achieved.
Establish a torque auditing program
Torque auditing validates the fastening process
Use common torque testing methods
Measuring torque occurs in three areas of the assembly process
There are three universal torque testing methods that were established to provide a reference to the applied torque.
Your partner’s at Meyer Gage offered some insight into selecting the right gauge for your job.
When using plug gauges for GO / NO-GO inspection, the GO member should fit into the work piece to indicate to the operator that the component meets the correct specifications. For this reason the GO gauge is usually selected close, but above the lower limit size of the component.
The NO-GO member should not fit into the work piece. If it does, this indicates to the operator that the component has been machined incorrectly and is out of specification. The NO-GO gauge is usually selected just under the high limit of the component, so as to stay within the part’s upper and lower tolerance.
Application Example: To check the center hole in the component for later mounting to center arbor for grinding.
Attribute to Check: Center hole bore diameter.
Center Hole Specification Limits: 0.235″ to 0.245″
The GO / NO-GO gauge is a quick, easy way to verify if this center hole is bigger than 0.235″ yet smaller than 0.245″.
In addition to the proper numeric size as illustrated above, the class of gauge also needs to be selected when ordering gauges. This selection process should be based on ANSI Standard B22.214.171.124-2001 (Plug Gage Tolerance Selection Guide) Our website offers a tolerance calculator to help with this selection of class such as ZZ, Z, X, XX. Gagemaker’s Tolerance Chart
Raw Material and Heat Treatment Stabilization Process
Gauge material and heat treatment plays a very important role in obtaining a dimensionally stable and long life gauge. We use an OHNS Tungsten quality oil hardened non shrinking steel or a 20MnCr5 steel (for small thread rings). The gauge material is duly carburized hardened and tempered. A cryogenic treatment is carried out to increase the performance of the material. This cryogenic treatment is not a substitute for heat treatment, but rather an extension of the heating, quenching and tempering cycle. The process involves a slow controlled cooling, holding at cryogenic temperature for a specific hold time and then allowing to return to room temperature slowly. This process transforms all retained austenite to martensite. The end result is a very stable material which is 100% martensite and very hard RC 58-62. Without cryogenic treatment these steels may contain significant amounts of retained austenite which is a weak, soft, easily abraded micro constituent of steel.
CNC Precision Matrix Thread Grinding Machines
All API 5B/7-2 are precision ground on CNC grinding machines. These Grinding machines are state of the art in grinding technology.
Precision Hand Lapping
When necessary hand lapping is the finishing process that removes small amounts of material from the gauge surface to bring it within its final tolerance limits. It is the final procedure when machines cannot do the job, and of paramount importance. This process of feeling a millionth’s of inch is a true art.
Temperature Control & Traceability
All our gauges go through final inspection in a temperature controlled (20 degrees +/- .5 degree C) metrology lab. All API Master gauges are fully traceable to either NIST or NIM . Our long form certificate of inspection provides as much detail as possible showing evidence of dimensional compliance. We understand quality system documentation as well as value associated with it; and as a result we provide long form certificates FREE with every gauge we sell regardless of price.
Coated & Uncoated Threaded Components / Parts
If the threaded components like nuts and bolts have to be coated then it is necessary to check them prior to coating. The gauge can be suitably designed to check the before coating size depending upon the coating thickness. Normally it is only the go limit gauge which is necessary to be used for checking before coating. The component near to nogo limit automatically falls within the tolerance limit after coating.
Normally coating thickness 0.001″. Here the thickness is considered as either an increase or decrease in the pitch diameter. If the coating thickness considered normal to the thread flanks, the variation in diameter is four times the thickness for threads with 60 degree angle and slightly less for 55 degree.
How to Determine and Select the Proper Tolerance for Your Gauging Application
The normal rule of practice requires 10 % of product tolerance to divided between the ‘GO and NOGO”gauges. For plug gauges, a plus tolerance is applied to the GO member and a minus tolerance to NOGO member. Ring gauges receive reverse tolerance direction so that the GO member is a minus an the NOGO is plus tolerance. Applying this result practice results in gauge tolerance always being included in the part tolerance by up to 10%. This results in the possibility that 10% of good product could fail inspection that no bad product would ever pass.
GAGEMAKER’S TOLERANCE CHART
(PLAIN PLUG & RING GAUGES)
TO & INCLUDE
* Table 1, pg. 4 of ANSI B89.1.6 2002 specifications
Proper Care Usage of Gauges
Parts Dimensions to be gauged should be free of burrs to prevent gauging interference.
Gauges should be turned or pushed slowly and gently. Forcing gauges will result in faulty gauging and possibility of damaging both the gauge and the part.
At Northern Gauge we provide a solid ring design because we know that it is superior to AGD (American Gauge Design) for the following reasons:
Dimensionally more accurate; we can physically measure the pitch diameter and minor diameter. AGD rings are never truely round. AGD ring Pitch Diameters are based on the pitch diameter of the set plug. So basically you only know it’s larger than the Pitch Diameter of the Set Plug; how much larger nobody knows for sure.
No setting plug needed for calibration or Manufacture; a cost saving as you are not forced to purchase the set plug if the gauge manufacturer doesn’t have it in stock.
More care-free, if dropped it doesn’t have to be re-calibrated. With the price of AGD setting plugs it make’s good economic sense to go with a solid ring and perform your periodic calibration based on usage.
Our solid rings are economically priced in comparison to AGD style.
Once you try using our solid rings you’ll never go back to AGD.
Gauge need to be thoroughly cleaned before and after use with either Alcohol or suitable solvent which do not contain water or leave an oil buildup.
Starrett M1 oil should be used when gauges are not in use. Do not use WD40 as it leaves a greasy buildup; really bad on gauge blocks.
The component must also be clean and free of metal particles.
Do not use thread gauges forcefully: like a tap or die.
Do not allow the gauge to be dropped on the shop floor, the gauges are brittle and may break.
Please note that the limit gauge is a precision tool and should be handled carefully.
It is very difficult to predict gauge life. Gauges used against cast iron, aluminum and stainless/duplex steels have faster wear due to lapping effect of these material . However, gauge life can certainly be improved by proper use and care of the gauges as defined above. A calibration interval of one year to start and adjust after a history is established.
A working gauge answers/enters the components but the inspection gauge doesn’t answer:
This is normally due to the size of the inspection go gauge slightly above the working go gauge. In such case the working gauge dimensions may be worn out or gauges are at either ends of the gauge tolerance. For future use, interchange the working and inspection gauges; and decrease your calibration interval.
Go gauge doesn’t enter but the nogo answers freely:
This occurs due to major diameter of nut i.e. internal thread or minor diameter of bolt i.e. external thread is not maintained properly The major diameter of the go plug and minor diameter of the go ring gauge is sharp and hence obstructs with the corresponding diameter on the component. Hence the operator takes more material without correcting the tool sharpness. The nogo major diameter/minor diameter being more truncated than the go gauge, enters the component. The go gauge controls all the thread parameters and will not enter if any of these are incorrect. If there is no control on the actual point of error, the effective diameter of the component becomes oversized and the nogo gauge enters.