A basic hole is defined as one where_________________?
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Answer: B. whose lower deviation is zero
Explanation
A basic hole is defined by international ISO tolerance standards as a hole whose lower deviation is zero. This means the minimum allowable limit of the hole size equals its specified basic nominal diameter. All manufacturing tolerances for a basic hole system are applied as positive allowances above the nominal size. ISO fit systems use basic hole and basic shaft systems to standardize interchangeable manufacturing clearances. Deviations represent the algebraic difference between a size limit and its corresponding basic nominal size. Basic hole systems typically pair a constant hole tolerance zone with varying shaft sizes to achieve different fits.
Option A is incorrect because upper deviation being zero defines a basic shaft rather than a basic hole. Option C is wrong because having both upper and lower deviations at zero would leave no manufacturing tolerance. Options D and E are false because basic holes are fundamental and well established in engineering metrology.
- Subject
- Engineering
- Category
- Mechanical Engineering
- Topic
- —
- Difficulty
- medium
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