A Non-standard Precision nut has a range of tolerances. The basic deviation is the distance from the zero line of the shaft or hole to the specified tolerance value. In general, basic deviations of a nut should be as close to zero as possible. There are 28 different basic deviations stipulated by the national standard for shafts and holes. They are given in the attached table and are represented by Latin letters. The basic deviation ranges from a-h for upper deviation to js for lower deviation.

Before buying a non-standard precision nut, you must conduct a thorough study of the specifications and drawings of the non-standard product. You should use CAD software to analyze the parts, including their shapes and dimensions. You should also carry out a quality inspection of the finished products.