Air Gaging Tips
Over the years, the tooling for air gaging has remained basically the same: steel tubes or rings with precision orifices that set up a pressure/distance curve when in use.
Conventional air gaging for measuring inside diameters is typically limited to a minimum size of about 0.060"/1.52mm: below that, it becomes difficult to machine air passages in the plug tooling, and to accommodate the precision orifices or jets. But air gaging is among the most flexible of inspection methods, and with a simple change of approach, it can be used to measure very small through holes, below 0.040"/1mm in diameter.
Air gaging represents the method of choice for most high-resolution measurements on large production runs. While quite durable and reliable compared to mechanical gages, air gaging is not care-free.
When most people think of air gaging, they think of plugs. But a number of air ring and air fork styles provide the same benefits and some additional ones as well.
Let's now consider measuring blind holes and counterbores with plug-type gages. Both types of holes are gaged similarly, so for the sake of economy, I'll use the term "blind hole" throughout.
The right angle is one of those things that man has created in his mind. In nature it only happens by chance. But the importance of this concept—which results from the perpendicular intersection of lines or surfaces—applies to many things, including architecture, civil engineering, agriculture, and manufacturing.
Air gaging was the earliest form of sub-micron measurement available, and many of the air plug configurations developed during this period have not changed dramatically since then.
"Air gaging is the greatest thing since sliced bread," a friend once told me. And he was right — air gaging is good. It's fast, high resolution, non-contact, self-cleaning and easy to use. For use in a high-volume shop, it's hard to beat.
In a high volume production environment, the cost of gaging is related to the speed with which measurements can be made and how fast results can be interpreted. Let
One of the challenges that often comes across my desk is the request to measure a tight tolerance on an ID or OD that is on a very narrow land. Often, this dimension needs to be measured in fairly high volume and frequently in the machine.
Air gages are capable of measuring to tighter tolerances than mechanical gages. The decision break-point generally falls around 0.0005”; if your tolerances are tighter than that, air gaging provides the higher resolution you will need.
There are numerous parts that make use of very small holes in various industries (or in your garage). I can think of maybe a dozen, but the most common ones seem to be aerosol cans, needles for delivering fluids and medicines, fuel injection nozzles, and simple fixed restrictors used to control liquid or air flows.