Microscope 216 Coarse Focus Mechanism
Coarse focus is the typical rack and pinion mechanism, but with spiral cut threads. Spiral rack and pinion was popularized by J. Swift & Son of the late 1800s. Spiral threads yielded two advantages over horizontal threads:
1) There is more contact between the pinion and rack, giving greater durability, and lower backlash.
2) The pinion threads roll onto the rack incrementally, thus yielding a smoother action.
1) There is more contact between the pinion and rack, giving greater durability, and lower backlash.
2) The pinion threads roll onto the rack incrementally, thus yielding a smoother action.
This microscope has a stop tab at the top of the rack.
"12" stamped inside the coarse mechanism