This series is the first international standard (ISO-2982) approved in 1971 after eight years of cooperative effort among many nations of the world.
To meet the variances of some nations using metric dimensions and to bring the quality of manufacture to United States standards, this series is manufactured with a thread of 4H tolerance grade and position as promulgated by the International Standards Organization. Still these locknuts are fully interchangeable with metric locknuts made to a 5H tolerance grade and position. Be aware, however, there are special thread metric retaining locknuts just as there have been and their will be special inch locknuts for the special engineer and special application.
The runout of the bearing face to the pitch diameter of the threads has a one revolution total indicator reading of no greater than: 25 Microns (.001 inches) for sizes 00 through 10, 50 Microns (.002 inches) for sizes 11 through 20, 100 Microns (.004 inches) for sizes 21 through 40.
These metric locknuts come in carbon steel. Sizes KM-44 and larger are a Whittet-Higgins design and have class 7H metric trapezoidal threads. They use a PPM precision locking plate instead of the lockwasher. These locknuts can also be used in place of the HM31xx series locknuts.
As with all precision retaining devices, care must be taken during assembly to assure premium performance. Please open and review our installation instructions for proper technique and best results.
United States 
