CFS Fastener Selection & Application 2 — Questions and Answers
Question 1: Which fastener type is best suited for joining two thin sheet metal panels where access is only available from one side?
- Hex cap screw
- Blind rivet (pop rivet) (Correct answer)
- Carriage bolt
- Stud bolt
Correct answer: Blind rivet (pop rivet)
Blind rivets are designed for one-sided access applications where the back of the joint is inaccessible.
Question 2: A fastener is needed to connect wood to masonry in an outdoor environment. Which option is most appropriate?
- Standard zinc-plated lag screw
- Hot-dip galvanized lag screw (Correct answer)
- Stainless steel machine screw
- Cadmium-plated bolt
Correct answer: Hot-dip galvanized lag screw
Hot-dip galvanized fasteners provide superior corrosion protection for outdoor wood-to-masonry connections.
Question 3: When selecting a fastener for a joint subject to significant vibration, which feature is most important?
- High tensile strength
- Locking capability (Correct answer)
- Fine thread pitch
- Large head diameter
Correct answer: Locking capability
Vibration loosening is the primary concern, so locking features such as nylon inserts, serrated flanges, or lock washers are critical.
Question 4: Which thread form is standard for general-purpose fasteners in the United States?
- Metric ISO (M)
- Unified National (UN) (Correct answer)
- British Standard Whitworth (BSW)
- ACME
Correct answer: Unified National (UN)
The Unified National thread system is the US standard for general-purpose fasteners, encompassing UNC, UNF, and UNEF series.
Question 5: A bolt is specified as 1/2-13 UNC Grade 5. What does '13' represent?
- Thread length in millimeters
- Threads per inch (Correct answer)
- Tensile strength in ksi
- Bolt length in sixteenths of an inch
Correct answer: Threads per inch
In the designation 1/2-13, '13' is the number of threads per inch (TPI) for that diameter.
Question 6: For a flanged joint on a pressure vessel, which bolt pattern consideration is most critical for uniform sealing?
- Using the fewest possible bolts
- Applying bolts in a star or cross pattern during tightening (Correct answer)
- Tightening bolts in a clockwise sequence
- Selecting bolts with the largest possible diameter
Correct answer: Applying bolts in a star or cross pattern during tightening
A star or cross-tightening pattern distributes clamping force evenly across the gasket, preventing leaks.
Question 7: Which fastener material is preferred when electrical conductivity must be minimized in the joint?
- Aluminum alloy
- Brass
- Nylon (polymer) (Correct answer)
- Titanium
Correct answer: Nylon (polymer)
Nylon and other polymer fasteners are non-conductive and are used in electrical and electronic applications to prevent current paths.
CFS Fastener Selection & Application 2
Which fastener type is best suited for joining two thin sheet metal panels where access is only available from one side?