Just trying to figure this out - when I dimension a circular feature I'll get one size but when adding a GD&T dimension for that same exact feature I get a different size altogether (example below). What's the reason for this?
Legacy dimensioning, Calypso, Geopak/Mcosmos and many other, older CMM software packages all use least squares. That wasn't necessarily because it was right from a standards perspective, it was because it is a comparatively easy calculation to perform that is reasonably well understood and because NIST and the PTB offer certification for least squares math. As I frequently have to remind my kids - just because everyone else is doing something, it doesn't make it right.
In introducing the Geometric Tolerance command, Hexagon's intention was not to "make things worse", it was an attempt to give many of our users what they had been asking for - full compliance to standards. Some of the most common questions we are asked by new customers is "does your software comply to ASME / ISO" and "does your software support GD&T".
Legacy dimensioning, Calypso, Geopak/Mcosmos and many other, older CMM software packages all use least squares. That wasn't necessarily because it was right from a standards perspective, it was because it is a comparatively easy calculation to perform that is reasonably well understood and because NIST and the PTB offer certification for least squares math. As I frequently have to remind my kids - just because everyone else is doing something, it doesn't make it right.
In introducing the Geometric Tolerance command, Hexagon's intention was not to "make things worse", it was an attempt to give many of our users what they had been asking for - full compliance to standards. Some of the most common questions we are asked by new customers is "does your software comply to ASME / ISO" and "does your software support GD&T".
