Understanding GD&T

designing and building any kind of mechanical system is a complex process that needs to properly account for many different parameters like cost materials and Manufacturing techniques but one of the key challenges is making sure that all of the parts once manufactured will fit together and function as intended and that's why tolerancing is such an

important part of the mechanical design process the easiest way to define tolerances is using the dimensional approach where drawings Define how much each dimension of a part is allowed to deviate from its nominal value but dimensional tolerancing doesn't work particularly well in a lot of scenarios because it doesn't really reflect how the part will be used

it doesn't let you specify that you need a surface to be flat because it has to create a seal with another part for example or let you control how close to perpendicular the axis of a hole needs to be to the surface it's drilled into

geometric dimensioning and tolerancing usually called gdnt is a different approach to tolerancing that allows you to control tolerances in a way that reflects the intended function of the part it complements dimensional tolerancing by letting you control 14 different geometric characteristics helping you better communicate which aspects of your design are important these characteristics can be split into

categories that control form orientation location profile and run out unlike the traditional tolerancing approach that applies tolerances to Dimensions gdnt applies them to Features instead a feature could be a surface a hole or a slot for example it's important to differentiate between surface features which are just individual surfaces and features of size which are any