Limits and Fits — Define a Basic Hole According to the hole-basis system of limits and fits, a “basic hole” is defined by which deviation condition?

Introduction / Context:
Limits and fits standardize permissible size variations to ensure interchangeability. The hole-basis system fixes the hole’s lower limit at the basic size, while the shaft deviations vary to obtain different clearances or interferences.

Given Data / Assumptions:

• Hole-basis system (commonly used in design and manufacturing).
• Basic size is the nominal dimension used for the tolerance framework.
• Deviations measured from the basic size: upper (ES) and lower (EI) for holes.

Concept / Approach:
In the basic hole system, EI (lower deviation) = 0. The tolerance zone for the hole extends upward from the basic size by the prescribed tolerance amount. Shafts are assigned deviations to create required fits (clearance, transition, or interference).

Step-by-Step Solution:
Define basic hole: EI = 0 → minimum hole size equals basic size.Upper deviation ES is positive for clearance fits, zero for H7 basic hole with zero upper tolerance? No; ES defines the upper limit relative to basic size and varies with tolerance grade.Thus the defining condition is “lower deviation is zero”.

Verification / Alternative check:
Standards such as ISO system of limits and fits designate hole basis with letter H (EI = 0).

Why Other Options Are Wrong:
Upper deviation zero corresponds to a specific case (basic shaft g/h), not the hole-basis definition.Both deviations zero would imply zero tolerance, impractical.Other statements do not reflect the standardized definition.

Common Pitfalls:
Confusing hole-basis (EI = 0) with shaft-basis (es = 0 for shafts).

Final Answer:
lower deviation is zero