In manufacturing industry, someone once estimated that there are more circular workpieces than flat workpieces, ranging from screws, nuts, washers, to cylinders and bearings, and application of circles is indeed very high.

 

Measurement example of a circular workpiece
For these rotating parts, the most urgent problem is how to evaluate their true circular "shape". Today, editor will introduce symbols and definitions related to roundness (reference standards: ISO/DIS 1101:2017, ISO 5459).

Extraction circle shall be confined within tolerance zone between two coplanar concentric circles with a radius difference t.

 

Edge extracted from cylindrical surface shall be limited to tolerance zone between two parallel straight lines in specified direction and distance t.

 

Is area between two parallel planes separated by a tolerance value t.

 

Extraction cylindrical surface shall be confined within tolerance zone formed between two concentric cylindrical surfaces with a radius difference t.

 

Extraction center of circle shall be limited within tolerance zone formed by a circle of diameter t concentric with reference.

 

Extraction axis shall be defined within tolerance zone formed by a cylindrical surface of diameter t coaxial with reference.

 

Extraction axis shall be limited to a tolerance area formed by a cylindrical surface of diameter t perpendicular to reference plane.

 

Extraction surface shall define a tolerance zone formed between two parallel planes at a distance t and perpendicular to reference axis.

 

In any section perpendicular to reference axis, extraction line shall be defined within tolerance zone formed between two coplanar concentric circles whose radius difference is t and whose center is on reference axis.

 

On any cylindrical section coaxial with reference axis, extraction circle shall be confined within tolerance zone (on cylindrical surface) formed between two equal circles at an axial distance t.

 

Extraction surface shall be defined within a tolerance zone formed between two cylindrical surfaces with a radius difference t and coaxial with common reference axis.

 

Extraction surface shall be defined within a tolerance zone formed between two parallel planes at a distance t and perpendicular to reference axis.