What it covers
The material is split into 14 topics, running from position at RFS and at MMC with bonus tolerance, through datum precedence, Rule #1 and the form, orientation, profile and runout controls, to composite position and how parts are gaged and inspected. It is meant for machinists, inspectors and engineers who have to read feature control frames on real drawings.
Where the numbers come from
The evaluation is this site's own code, written to follow ASME Y14.5-2018. None of the standard's text, tables or figures is reproduced, and where it can reasonably be read more than one way the guides say so. The worked examples in the 14 guides are computed by the same evaluation functions the workspace runs, and each guide has a link that opens its example in the workspace so you can change the inputs. The 156 practice questions were written for the site.
Who makes it
One independent developer builds and runs DatumLab. That developer keeps a few other engineering references as well, among them OpticBench, PressBench, EngiRef and ThreadRef.
The guides are signed “By DatumLab” with no individual byline, and their markup gives the site's organization as author. No engineering or metrology credential is claimed.
Where DatumLab stops
It is a study and checking aid. It is not an inspection record, a released drawing or a certificate of conformance, and it does not replace the controlling drawing, a calibrated instrument or a CMM report. Whether a part is accepted is decided by your quality system against the drawing it was made to. A verdict here is a second look at the arithmetic.
Start with the workspace, the guides, the practice questions or the symbol reference. Questions: [email protected]. See also privacy and terms.