CFS Fastener Testing & Quality Control 3 — Questions and Answers
Question 1: What does the term 'lot traceability' mean in fastener quality control?
- Tracking a fastener from raw material heat through finished product (Correct answer)
- Verifying coating color consistency across shipments
- Measuring dimensional tolerances on every part
- Confirming the distributor's invoice matches the PO
Correct answer: Tracking a fastener from raw material heat through finished product
Lot traceability links each finished fastener lot back to the raw material heat, manufacturing records, and test data for accountability.
Question 2: A torque-tension test on a fastener assembly shows high clamp load variation. Which variable is most likely responsible?
- Bolt head height variation
- Coefficient of friction between mating surfaces (Correct answer)
- Thread pitch diameter within tolerance
- Bolt length variation within specification
Correct answer: Coefficient of friction between mating surfaces
Friction at the bearing face and in the threads accounts for approximately 90% of applied torque, so friction variation causes significant clamp load scatter.
Question 3: Which destructive test is specifically designed to detect seams, laps, or folds in the head of a bolt?
- Proof load test
- Macro etch examination (Correct answer)
- Vickers hardness traverse
- Salt spray test
Correct answer: Macro etch examination
Macro etch (or cross-section examination) reveals internal discontinuities such as seams and cold-working defects in bolt heads.
Question 4: What is the significance of the 'acceptance quality limit' (AQL) in fastener inspection?
- Maximum allowable hardness in a lot
- Percentage of defectives considered acceptable for a lot to pass (Correct answer)
- Minimum tensile strength for a grade
- Thread engagement length requirement
Correct answer: Percentage of defectives considered acceptable for a lot to pass
AQL defines the maximum percent defective (or defects per hundred units) that is still considered acceptable for routine sampling inspection.
Question 5: A hydrogen embrittlement susceptibility test requires fasteners to be loaded at what percentage of their proof load?
- 25%
- 50%
- 75% (Correct answer)
- 100%
Correct answer: 75%
Per ASTM F1940 and similar standards, sustained load tests for hydrogen embrittlement detection are typically conducted at 75% of proof load.
Question 6: Which document must accompany a shipment of fasteners to certify compliance with a specific ASTM standard?
- Bill of lading
- Certificate of conformance (C of C) (Correct answer)
- Packing list
- Purchase order acknowledgment
Correct answer: Certificate of conformance (C of C)
A certificate of conformance formally attests that the fasteners meet the requirements of the referenced specification and includes test data or mill records.
Question 7: What condition is being checked when a thread gauge 'GO' ring gauge passes but 'NO-GO' ring gauge also passes on an external thread?
- Thread is oversized beyond the maximum material limit (Correct answer)
- Thread is undersized below the minimum material limit
- Thread pitch is incorrect
- Thread surface finish is too rough
Correct answer: Thread is oversized beyond the maximum material limit
If the NO-GO gauge passes, the thread pitch diameter is below the minimum material condition, meaning the thread is undersized.
CFS Fastener Testing & Quality Control 3
What does the term 'lot traceability' mean in fastener quality control?