Fits and tolerances: what term denotes the range of tightness or looseness that results from specified allowances and tolerances when two mating parts are assembled (for example, a shaft and a hole)?

Difficulty: Easy

Correct Answer: Fit

Explanation:


Introduction / Context:
Mating parts require controlled relationships to ensure function—rotation, sliding, or interference installation. Standards define how much clearance or interference is acceptable.



Given Data / Assumptions:

  • Two parts: typically a shaft and a hole.
  • Drawing specifies limits and allowable variation.
  • We need the term that encapsulates the resulting assembly condition.


Concept / Approach:
“Fit” describes the assembly condition (clearance, transition, or interference) produced by manufacturing variation within stated limits. Allowance is the intentional minimum clearance or maximum interference; limits are the permitted size extremes of each feature.



Step-by-Step Solution:

Identify that the question refers to the assembly condition between features.Recall definitions: fit vs. allowance vs. limits.Select “Fit” as it describes the range of tightness/looseness in assembly.


Verification / Alternative check:
Check ISO or ANSI fits tables (e.g., H7/g6) that classify fits by functional behavior—those are fit designations, not just limits.



Why Other Options Are Wrong:

  • Limits: size boundaries for individual parts, not the assembly relationship.
  • Specifications: broad term; lacks specificity to assembly condition.
  • Allowance: the minimum intended clearance or maximum intended interference, not the overall range.


Common Pitfalls:
Interchanging “allowance” and “fit.” Allowance is a single-value design intent; fit is a category/range outcome.



Final Answer:
Fit

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