The nominal spindle diameter is a dimension frequently used to identify threaded spindles. In most cases, the outer diameter of the spindle corresponds to the diameter over the thread crests.
The nominal diameter is not a measured value, but a design and designation dimension. In most standard systems (e.g., ISO or DIN), it corresponds to the outer diameter, but can also deviate slightly for special thread forms.
Practical Example
For our ball screw drives KGT 25 × 5 × 1000 mm lg., the outer diameter is 24 mm and the nominal diameter is 25 mm.