7.2.3 Dimensions, Allowances and Tolerances Flashcards
What must an aircraft maintenance engineer always consider?
The dimensions, allowances, and tolerances they are working to.
What is a dimension?
A measurable limit of some kind, such as length, width, or height.
What is a limit dimension?
The maximum or minimum dimension of a machined part or component.
What is the nominal size of an item?
An approximate dimension used for general identification.
What is the basic size?
The theoretical size from which size limits are derived by applying allowances and tolerances.
What is tolerance?
The total amount by which a given dimension is allowed to vary.
How is actual size confirmed to be within tolerance?
By measuring the actual size of a part against the known basic size and tolerance.
What is an example of a basic size and tolerance?
The diameter of a bearing shaft is 4 in with a tolerance of +/- 0.005 in.
This means the actual size must be between 3.995 in and 4.005 in to be within tolerance.
What are bilateral tolerances?
Tolerances that can be added to or subtracted from the basic size.
What are unilateral tolerances?
Tolerances that only have a tolerance in one direction from the basic size.
What is clearance in terms of fit?
The space between the mating parts.
What is a clearance fit?
A fit that allows for sliding or rotating between the parts.
What is an interference fit?
When the dimensions of two parts overlap.
What is an allowance?
The minimum clearance space intended between two parts.
What does workmanship refer to?
The skill of a craftsman, quality of the product, and attitude towards care.
