GD&T Profile of a Surface (Basics)

We’ll first look at Profile of a Surface as it is the most common of the two, and likely what you’ll use. Profile of a surface defines a Tolerance zone between two equidistant reflections of the defined surface. Essentially, if your profile of a surface TZ was .06mm, you could take your CAD model, and then create a version of it .03mm smaller and .03 mm larger and those would be the boundaries of your TZ. Every point of your part would then need to fit within that tolerance zone. Profile of a surface is useful for parts that are not easily measured with calipers or through rotation. A way to help remember that is Profile of a surface is useful for any part that needs to be ergonomic, aerodynamic, or just plain look cool. For those parts, it is unlikely that simple rotation, caliper measurements, or other callouts will work. Ergonomic parts could include grips, saddles, and chair surfaces. Aerodynamic parts are plane wings, rotor blades, and any part with an aero foil shape. Just plain cool parts