Mechanics need a digital micrometer. This is a rock solid, dependable and economical tool.
Calipers are not enough.
Accuracy in spoke threads, in axles, in suspension pivots, in hydraulic assemblies requires precision to 0.001mm.
I was an overachieving bike mechanic for 30yrs without owning a micrometer. Today it’s a necessity for me. We’ve all depended on vernier calipers but, frankly, we often called them “guess sticks.” They are made to a variety of qualities, regularly nearly given away as promotions, and frequently barely work. They read to the third (0.001mm) or fourth place but are often not dependable to 0.01mm. At times we need better.
Spoke threads are an example—wire for 2.0mm spokes varies from 1.97 to 2.02. You need to detect and understand this. Builders report oval wire in blanks—can you find these? Thread outside diameter identifies how deep or shallow the thread form which affects building.
Especially for axles and pivot shafts, we need 0.001mm accuracy. When bearings are involved, such measurements are essential. Hydraulic pistons and bushings are likewise precise beyond verniers.
Would be nice to own a vast set of micrometers but start with the one you’ll use 90% of the time, 0-1″ (0—20mm).