Here is a tiny turned roller for a medical device assembly machine.
Only 6 were needed, making this project unattractive for bigger vendors to tackle.
The body of the roller is 4 mm diameter and precision turned on my Prodigy CNC lathe to a 16 micro-inch finish.
The shafts were fitted into a precision wire EDM cut and diamond lapped bore, positioned to length using a 50:1 shadowgraph, and then swaged in place.
Here is a pivot shaft before installation; it’s quite a challenge to handle, and small enough to be lost forever if it’s dropped on the floor. (0.0205” diameter and 0.093” long)
2 pivot shafts, precision ground to length, and installed back-to-back, were used in each roller
The shafts were sourced commercially, and run in jewel bearings with almost zero friction.
The tip geometry is almost impossible to make without special equipment (0.001” radius and 2 micro-inch finish).
It’s also very delicate, even though the pivots are hardened, so sliding commercially available pivots into a machined hub and then swaging them in, became the process of choice to avoid damaging the tips during installation.
Attempts to press them into an undersized bore were unsuccessful.