In continuing our series on GD&T callouts, today's Metrology Minute focuses on Flatness. Flatness is a very simple callout that focuses on just how flat a particular surface is without making reference to any specific datum. Very often, a Flatness callout can determine whether a job shop is able to face mill a surface to its finished dimension or if grinding and perhaps outside services are required to achieve the necessary Flatness. If a specific [...]
In continuing our Metrology Minute focus on GD&T, this month we will discuss Runout and Total Runout. Simply defined, Runout is how much a model feature varies with respect to a datum when the part is rotated about the datum’s axis 360 degrees. The datum in question would necessarily be an axisymmetric feature. It generally involves the analysis of a circular feature that is created when taking a single point tool and rotating it around [...]
The Benefit of using GD&T and a Positional Tolerance vs +/- Tolerances When creating a part like the one below, the intent of the four holes is likely to fasten this component to another in the final assembly where the round holes will accept round fasteners. We want to look for a way to maximize our tolerance to provide as few scrapped parts as possible. A typical dimensioning scheme using +/- tolerances might look something [...]
