Air gauges compared to mechanical gauges
Air gauges are often simpler and cheaper to engineer than mechanical gauges and they do not require linkages to transfer mechanical motion so that the jets can be spaced very closely at virtually any angle. This allows the air gauges to handle tasks that are often too difficult or expensive for mechanical gauges.
Air gauges are very flexible and you needn’t be an engineer to understand how to simplify the gauging tasks. Almost all kinds of measurements whether dimensional or relational can be performed with air. It is also suggested to use air for more complex measurements. However, for the machinists, the mechanical gauge will be the preference because it is straightforward but air gauges are more capable of measuring tight tolerances than mechanical gauges. Air gauges can handle 50 millionths with ease while some can measure resolution of 5 millionths. At their very best, the mechanical gauges are also capable of measuring down to 50 millionths but it should be handled with great care.
The high pressure jet of air gauges cleans the surface of the workpiece of most coolants, chips and grits which saves the operator time in cleaning. Mechanical gauges can become clogged with oil and coolant and may require frequent disassembly for cleaning. The internal workings of mechanical gauges are subject to wear. On the air plug gauges, only the plug will show signs of wear but it has a large surface area so wear occurs rather slowly.
Maintenance requirements for air gauges
In order to maintain accuracy, air gauges require proper maintenance of tooling and strict vigilance over air supply. Although factory air can be controlled, compressors and air lines are usually shared by others which require that the air reaching the gauges to be ensured as clean. Air gauges must always have a filter in place when operating and it should be immediately changed when saturated. Air leaks are the common causes of inaccuracy in measurements. In order to test, cover the measuring jets tightly with your fingers and watch the indicator needle carefully. If it is not stationary, check all fittings, tubes and connectors for any leaks. Most of factory air lines run at about 100 psi but depending upon the demands of other users, this can fluctuate rather quickly. Properly designed air gauges run reliably over a wide range – some as wide as 40-150psi – so that a certain amount of fluctuation can be easily handled. Other air gauges can be quite sensitive which may require a dedicated air line.