Mechanical

GD&T Symbols List Flatness Flatness GD&T Flatness is a common symbol that references how flat a surface is regardless of any other datum’s or features. It comes in useful if a feature is to be defined on a drawing that needs to be uniformly flat without tightening any other dimensions on the drawing. The flatness tolerance references two parallel planes (parallel to the surface that it is called out on) that define a zone where the entire reference surface must lie. Straightness Straightness actually has two very different functions in GD&T depending how it is called out. In its normal form or Surface Straightness, is a tolerance that controls the form of a line somewhere on the surface or the feature. Axis Straightness is a tolerance that controls how much curve is allowed in the part’s axis. This is usually called out with an included call to maximum material condition. Both callouts are very different from ea...