Measurement of flatness, perpendicularity, and parallelism.ĬMM can perform many different types of measurements. Measurement of flatness, perpendicularity, and parallelism. Then, move the altimeter and parts so as to cover the entire length and width of the surface, and calculate the flatness variance of the actual surface.

Fix the part face down on the panel, and make the altimeter contact the designated surface through the hole on the panel. Machinists sometimes use panels to check flatness. We can’t measure it by simply placing the part on a plate or a slab and using an altimeter, because this means that we have to measure the parallelism with respect to the bottom surface. Two Sets of Parallel Planes where the entire referenced surface must lie.įlatness M easurement: Single Planar Surfacesįlatness measurement requires a platform and an altimeter, probe or some type of surface. It is represented by a parallelogram, and the box symbol can be read as “The surface must be located between two parallel planes, 0.2 to each other in all views. Geometric feature symbol used for flatness. The flatness tolerance applies to all drawing views, not just views that display tolerance annotations.Īn example of flatness is shown below. All points on the specified surface must lie between these two planes for part approval. The distance between these two planes is the flatness of the surface. The controlled surface must lie completely in the space between the two planes. The other is at the deepest point of any irregular surface. A vertex located at the highest irregularity on the surface. The tolerance zone for flatness tolerance is based on two parallel planes. It controls the extent to which the surface on the part may deviate from the ideal plane. It is a general symbol, it indicates the flatness of the surface, and has nothing to do with any other benchmarks or features. In this article, we will introduce flatness marking, tolerances, measurement methods, the difference between flatness and conventional tolerances and how to use it in the correct position to maximize efficiency. How do we design a surface that is not completely flat but flat enough to function properly? Flatness control tolerance.

Which surface is completely flat? In fact, no surface is completely flat.

Flatness gd&t symbol