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
By combining different hole and shaft tolerance classes, engineers create three primary types of fits:
ISO 286-1:2010(en), Geometrical product specifications (GPS)
(a–zc) are used for external features ( shafts ).
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