"When we think about comparative indicators, we usually are referring to dial indicators. However, test indicators also provide comparative measurements. The difference is that while dial indicators sense displacement that is parallel to the axis of the spindle, test indicators are designed to sense and measure displacements that are perpendicular to the shaft of the contact point."

"The most commonly used—and perhaps the simplest—measure of surface finish is the R_a parameter, or roughness average. But like ordering a coffee at one of today’s deluxe cafes, it’s not exactly simple. There are other things to consider in order to ensure the best results. For example, R_a can be measured with two types of contact gages, which are distinguished by the nature of the probe or contact that traverses the part’s surface. In 'skidded' gages, the sensitive, diamond-tipped contact (stylus) is contained within a probe, which has a metal skid that rests on the workpiece. These skidded gages use the workpiece itself as the reference surface."

Character Quote of the Month

"Gratitude is the memory of the heart." -  Jean Massieu

"Adjustable bore gages are comparative instruments. This means that the readout, whether it be a dial, digital indicator or other type of electronic readout, will show the amount and direction of variation in the test bore from nominal size. In this case, the gage needs to be set to the required nominal size to which the actual bore is to be compared.

Temper Your Expectations

"'When I was your age, I had to walk three miles to school every day – rain, snow, or shine!'

Why do parents strive to impress sons and daughters with their own childhood difficulties?  Why do men and women in leadership often respond to complaints with 'war stories' about their own hard knocks?"