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. Accurate air gaging requires proper maintenance of the tooling, and vigilance over the air supply. Although the factory air supply may not be under the gage…
Temperature fluctuations are one of the most common causes of measurement errors on parts with tight tolerances. As production tolerances become ever tighter and the error margin for measurement results constantly shrinks, this is an important issue that users may need to consider in their inspection process. The background to this is a natural physical…
Digital calipers are one of the most common hand tools used on the shop floor. In a manufacturing plant, under a quality control system, these tools need to be checked and calibrated on a regular basis. We have discussed in past articles the pros and cons of doing gage calibrations internally or by an external…
When measuring parts to tolerances of a thousandth of an inch, we can usually be certain that our measurements are accurate to within a “tenth,” if we follow standard gaging practice: i.e., master the gage frequently, maintain the gage in good working order, keep things clean, have the master recalibrated periodically, etc. But certainty becomes…
There are endless variations in the dials used on mechanical dial indicators. In most cases, though, they can be broken down into two distinct styles: balanced and continuous. There are endless variations in the dials used on mechanical dial indicators. In most cases, though, they can be broken down into two distinct styles: balanced and…
When we talk about differential gaging, we are usually referring to the process of using two sensing devices and combining the results into one measurement. The measured dimension is the change in the position of the two sensing components. Differential gaging has some advantages over normal, comparative measurements using a single sensing head against a…
As a method to get inspiration for topics for this column, I go back through old documents. As one can imagine, the basics of metrology were mostly developed in the early 20th century but have been refined and controlled to get where we are today. During this exploration I realized that we are rapidly closing…
Machinists working strictly in metal-working shops do not have many occasions to gage the thickness of soft materials. But many of our readers work in supporting roles, helping to build or maintain the machines that produce textiles, plastic films, paper and other products that are compressible. Even readers who work only with metals should realize…
WITH MASTER RINGS AND ENGAGEMENTS, SIZE MATTERS A master ring, or ring gage, is basically a bore of known dimension. The precision hole is often used as a setting master for variable inside-diameter gages (such as bore gages, air tooling and mechanical plug gages), for go/no-go mastering of fixed ID gages, and for go/no-go OD…
When we think about making a simple measurement, such as an outside diameter, many methods can be used. These would include calipers, micrometers, mechanical snap gages, air snaps, CMMs, and special fixture gages, just to mention a few. The problem with all these methods is that while each is good in its own right, there…