By combining different hole and shaft tolerance classes, engineers create three primary types of fits:
Indicates the position of the tolerance zone relative to the nominal (basic) size. iso 286 pdf
(a–zc) are used for external features ( shafts ). By combining different hole and shaft tolerance classes,
Standing for International Tolerance , these grades (from IT01 to IT18 ) define the magnitude or "width" of the tolerance zone. Lower numbers indicate higher precision. Common Types of Mechanical Fits iso 286 pdf
(A–ZC) are used for internal features ( holes ).
This part provides tabulated numerical data for limit deviations based on the nominal size of the part (up to 3,150 mm). Key Components of the ISO 286 System