Do I have to send in my master setting plug gage for you to calibrate my adjustable thread ring?
This is a fair and reasonable question. There is an impression that calibration companies have master setting plugs for every thread ring that is covered on their scope of accreditation. It would be extremely cost prohibitive for calibration companies to purchase master setting plugs for ALL possible thread rings that could be calibrated. In addition, the repetitive use of a master setting plug for numerous customers calibration would require frequent replacement due to wear and this would significantly drive up cost of operations. So, is there another option?
Direct Measurement of Adjustable Thread Rings
There are inherent problems when using direct measurement for the calibration of adjustable thread rings. Gage Crib published an excellent explanation of these problems in Ring Gage Calibration by Direct Measurement. We strongly encourage to read this article. They specifically mention the deficiencies of using a coordinate measuring machine -CMM in regards to helix offset and why a master setting plug is the preferred method.
You might also want to check out Thread Ring Realities in Quality Magazine- "The ASME standards to which these gages are made require them to be verified by their fit on an appropriate setting plug. There is no other option on the smaller sizes but different hardware for directly measuring pitch diameter is often used to get around the costs of a setting plug for non-stocked gages. Each method takes a different approach to the situation and because they are not the same from a metrology point of view, the ‘answers’ they produce are rarely the same either."
Indirect Measurement of Adjustable Thread Rings
This approach is very intriguing from a calibration point of view. Wouldn't it be great if you could somehow "look" at an adjustable thread ring and calibrate it! Visual measurement methods are used in a variety of manufacturing settings, but the current standard for thread rings does not support this approach. Larry Borowski has written an excellent article - Setting Adjustable Thread Rings- that explains why you really do need to send in your master setting plug when you have your adjustable thread rings for calibration.
Conclusion: Send in your master setting plug when you want your adjustable thread rings calibrated.
Want to know more about using threads? Check out these videos.