FAA Aviation Mechanic General (AMG)Materials, Hardware and ProcessesHard
A technician must fabricate a 90-degree bend in a piece of 0.032-inch aluminum sheet using a bend radius of 0.125 inch. Using the standard bend allowance formula BA = (0.01743R + 0.0078T) × N, what is the bend allowance?
- A0.281 inch
- B0.156 inch
- C0.125 inch
- D0.219 inch
Show answer & explanationAnswer & explanation
Correct answer: D. 0.219 inch
BA = (0.01743 × 0.125 + 0.0078 × 0.032) × 90 = (0.002179 + 0.0002496) × 90 = 0.0024284 × 90 ≈ 0.219 inch. This bend allowance value tells the technician how much material length is consumed by the bend, which is added into the flat pattern layout calculations.
Why the other options are wrong
- A. Overestimates the result; does not match the correct calculation.
- B. Does not match the formula's result for these values.
- C. Equal to the bend radius, not the calculated allowance.
Bend Allowance
The amount of material consumed by a bend, calculated with BA = (0.01743R + 0.0078T) × N, used to determine flat pattern layout length for sheet metal fabrication.
- R = bend radius, T = material thickness, N = bend angle in degrees
- Used with setback to determine flat pattern layout
- Essential for accurate sheet metal part fabrication
Memory trick: 'Bend Allowance eats up the flat length'