Lecture 12 - Mechanical Fasteners

Question 1

What 2 types of Mechanical Assemblies are there?

Answer 1

Methods that allow for disassembly (threaded fasteners)
Methods that create a permanent joint (rivets)

Question 2

What are the types of screws?

Answer 2

Machine screws
Cap screws (made from higher strength materials)
Set screws
Self tapping screws

Question 3

What purpose do washers serve and what types of washers are there?

Answer 3

Washer distribute stresses, provide support for clearance holes, protect part surfaces, increase spring tension, and resist unfastening.
the 3 types are flat, spring and locking washers

Question 4

Bolt strength is measured in 3 ways, by…

Answer 4

Tensile strength
shear strength
Proof strength (yield strength)

Question 5

What problems occur when a bolt is over tightened?

Answer 5

Stripping of internal or external threads
Bolt failure due to excessive tensile stresses on cross sectional area

Question 6

What methods are there for applying required torque?

Answer 6

Operator feel - no accurate, but adequate for most applications
Torque wrench - indicates amount of torque during tightening
Stall motor - motorized wrench that stalls at set torque requirement

Question 7

What are the basic parts of a rivet?

Answer 7

Mandrel head, rivet pin, rivet head, mandrel

Question 8

List all the types of rivets there are with advantages

Answer 8

Open rivet - Strong and low cost with wide range of use
Sealed rivet - provide water/air tight seal, better shear strength and vibration resistance
Multi-grip rivet - Wide grip range, vibration and moisture resistance
High Strength Multi-grip rivet - same as above with better tensile and shear strength
Split rivet - Split tail provides larger bearing area, wide range of fits and materials. softer material applications
Rivet nut - joins material while providing internal thread
Cup-Fix Rivet - multi-grip capability and fully sealed seam
Grooved rivet - for timber plastics or other fibrous materials
Peel Rivet - Mandrel peels rivet pin into 4 petals

Question 9

What are rivets used for and what are the advantages to using rivets?

Answer 9

Rivets are used for lap joints
Advantages are high production rates
simplicity
low costs

Question 10

What are some interference fit methods?

Answer 10

Press fit
Shrink and expansion fit
Snap fit
Retaining rings