What's Wrong With This Picture? On The Care And Feeding Of Master Rings And Other Metrology Artifacts

Quality assurance can only be as good as the measuring tools it relies on. It should be obvious that if you spend tens of thousands of dollars on a measuring machine, you need to protect this investment with routine maintenance and calibration. The same is true for hand tools and gages, which are the nervous system of a manufacturing operation's quality system.

So dial indicators, hand gages and their masters need to be regularly calibrated. Checking these tools against recognized standards assures their reliable performance and provides for traceability when nonconformity does rear its ugly head in the manufacturing process. As soon as the manufacturing team buys into this concept and a program of regular calibration has become a way of life, your company will have taken a big step forward on the road to cost reduction and profit enhancement. That's the big picture.

If your quality assurance program is working well, it means everyone is taking care of the little details that are ultimately so important. Those are the little pictures. Let's take a look at one. (See photo.)

Newly calibrated gages are generally packaged and transported back to the floor with great care. That's a 'no brainer'. But what about the tools and artifacts that are being sent back to the calibration room to be checked again? It's very important to remember that even though these gages are out of service, they are still precision measurement devices. As such, they need to be handled accordingly.

Very often we will see gaging come back for re-certification in the condition pictured. Or, even worse, the gages will be all thrown into a box with nothing to prevent them from banging together.

Under a microscope, one good scratch on an XX master ring can look like the Grand Canyon. We discover these canyons with alarming frequency at our Precision Measurement Center, where thousands of master rings and discs are measured every year. Many of these scratches result from the sort of treatment that the rings in the photo are subjected to.

If you don't think those rings are being abused, look again. For the most part, this packaging was carefully applied, but notice the wire on the tags. Now, in some cases there may be some plausible excuse for the marking of the rings this way. Maybe they are badly worn and are being sent back to be lapped and chromed back up to specification. However, even though the wire is soft, it still will mark and potentially scratch the part. Therefore, this type of packaging is never recommended.

A natural alternative is to attach an identifying tag with string. But don't do it! String tends to absorb rust-causing moisture. Stamping them with tool numbers is not the answer either. The stresses created in the metal can sometimes ruin a master.

However, don't give up; there are ways to mark the masters without risking damage. Some acceptable ways of identifying a master for shipment and inspection are to mark them with paint or a permanent marking pen, or include a sheet of paper that identifies the ring by its etched dimensions on the side. Even a sticky tag is a good temporary method of getting the ring identified until it reaches the source of recalibration.

A ring needs to be sufficiently protected whether it is traveling across the shop or across the country. It should be protected with an oil and plastic dip, individually wrapped and sturdily packaged.

The safest policy is to have one or more individuals trained in the proper handling, packaging and transporting of hand tools and masters for recalibration. This is a simple little detail that can pay for itself many times over during the course of a year. Most gaging equipment suppliers would be happy to provide you with the guidelines you need to bring this little picture into sharp focus.