Recently I provided a one day customized GD&T training to one of my customers, who’s been in pump manufacturing business for long time. Their drawings are very old school because you can tell from all those GD&T symbols, e.g. datum letter is before tolerance in FCF, etc..

A cylinder has a total of three surfaces: a top, bottom, and middle. The top and bottom, which are circles, are easy to visualize. The third is actually the curved wall of the cylinder. It is a surface that has measurable volume.

What is it?

Circles are simply closed curves. Where points along the curve converge to close the curve and the results are a circle.

With all instruments used for scanning, i.e. roundness machines and surface roughness gages, when scanning with a CMM the raw data must be filtered. When using a CMM to scan features on a part there are data filtering options that can affect the scanning results.

The software default selections may not always be the best option. As CMM programmers, when software messes with our data we better have a good understanding of what is going on with that data. Understanding filtering is key when faced with the multiple filtering options available.