GEOMETRIC FORM TOLERANCES OF SURFACES
There are many surface treatments in the manufacture of a machine part. Since the precise relationship of all surfaces with each other will increase the cost too much, it is ensured that the processing cost is reduced by ensuring only the precise processing of the relationship between the very necessary surfaces.

Only surface treatment marks and dimensional tolerances may not be sufficient to enable machine parts to be machined with the above mentioned precision. Example: Ensuring that a surface on a machine part is parallel or perpendicular to another surface of the same part within a certain tolerance, or that it is on the same axis with an ovality in a hole or another hole, cannot be achieved with only dimensional tolerance and surface treatment marks. In these cases, geometric shape tolerances should be used.

Geometric shape tolerances are indicated by symbols in side-by-side boxes.

The first box contains the symbol of surface relations such as linearity, parallelism, and perpendicularity.
In the second box, if the surface tolerance to be machined remains within a cylindrical region, the diameter symbol is given. This symbol is not used if it is a flat surface.
In the third box, the measure of precision is in millimeters.
In the fourth box, the method according to which the material will be processed is specified in order to achieve the specified sensitivity. See Table 5. If the method does not matter, this symbol is not used.
The letters indicating the referenced surfaces are given in the fifth box and on the right. These surfaces can be more than one (such as A, B, C)
Geometric Shape and Tolerance Representations are standardized with DIN ISO1101 norm. The main ones of these standards are given in the tables below. These

A- SHAPE TOLERANCES ……… ..…: (Table 1)
B- ORIENTATION TOLERANCES ………: (Table 2)
C- LOCATION TOLERANCES ……… ..: (Table 3)
D- DISCLAIMER (YALPA) TOLERANCES: (Table 4)
E- OTHER TOLERANCES ……………: (Table 5)

TABLE 1.

TABLE 2

TABLE 3.

TABLE 4,

TABLE 5,