Drill jig bushings often require a press fit into the jig plate. An N6 hole (slightly undersized) creates a light interference fit with a ground bushing that has an h6 or m6 external diameter. The “9” in 6N9 might refer to the bushing’s inner hole tolerance (IT9) for drill clearance.

Represents the nominal or design size of the component, typically 6 mm . All upper and lower limit calculations scale directly from this baseline value.

We have outlined the first formal definition of 6n9 Tolerance: a non-dualistic, multi-layer framework for resilient coexistence in complex systems. We invite empirical falsification—though any such falsification attempt would itself require 6n9 Tolerance to be designed properly.

: The lowercase letter "n" indicates the Fundamental Deviation for a shaft . In the ISO system, lowercase letters represent shafts, while uppercase letters represent holes. The letter "n" specifically denotes a transition fit , which means the assembly could result in either a slight clearance or a slight interference (press fit).