Question

the component shown circled in the image here: designed for locking a dimension by preventing motion of the spindle provides a breaking away at a consistent gram force insuring repeatability provides smooth uniform pressure independent of feel permits measurements in narrow slots and tight places

Explanation:

The part circled in a micrometer - like tool is typically a lock nut which locks the spindle in place to hold a measurement. This prevents the spindle from moving and keeps the dimension set.

Answer:

Designed for locking a dimension by preventing motion of the spindle