MIAE 313
Mechanical
Drawing and
Design
L EC T U R E 9 – FA S T E N E RS
WINTER 2025
1
Outline
• Keys, Splines and Serrations
• Pin Fasteners
• Retaining Rings
• Springs
• Rivets
• Welded Fasteners
• Adhesive Fastening
2
Methods to Fasten a Gear to a Shaft to Provide Transmission of Torque
3
Keys
In mechanical engineering, "keys" refer to machine elements designed to connect a rotating component to a shaft, enabling the transfer of torque.
Fundamental Function:
• Torque Transmission:
•
The core purpose of a key is to prevent relative rotational movement between a shaft and a component mounted on it (like a gear, pulley, or flywheel). This
ensures that rotational force (torque) is effectively transferred.
• Preventing Slippage:
•
Keys provide a positive connection, preventing slippage that could occur if the shaft and component were simply pressed together.
• Protection:
•
In some designs, keys are intentionally designed to be a "weak link." This allows them to shear or break under excessive load, safeguarding more expensive
machinery components from damage.
Key Features and Terminology:
• Keyway:
•
This is the slot or groove cut into both the shaft and the hub of the rotating component, where the key is inserted.
• Keyseat:
•
This term is often used to describe the portion of the keyway that is in the shaft.
• Keyed Joint:
•
This refers to the complete assembly of the shaft, key, and rotating component.
4
Keys - Types
▪
The most common types are shown in Fig. 11- 1-2.
▪
Square and flat keys
▪ Widely used in industry
▪ The width of the square and flat key should be
approximately one-quarter the shaft diameter
▪ These keys are also known as squared- taper or flattapered keys
▪ Proper key selection, refer Table 21 in the Appendix
▪
Gib Head Key
▪ Similar to square and flat key
▪ This has got a head for easy removal
5
Keys - Types
▪
The Pratt and Whitney key
▪ Is rectangular with rounded ends
▪ Two-thirds of this key sits in the shaft; one- third sits in the hub
▪
Woodruff keys
▪ Semicircular key fits in semicircular keyseat in the shaft and
rectangular keyway in the hub
▪ Width of the key is 1/4th the diameter of the shaft
▪ Diameter of this key is shaft diameter
▪ Half the key sits in the shaft and half the key fits into the hub
▪ The last 2 digits give the in 1/8th of an in and the digits before
last 2 give the width in 1/32 of an in.
▪ So the key here is 1210 that is 12/32 X 10/8 in. or 3/8 x 1¼ inch
6
Feature
Square Key
Shape
Rectangular, with
Square cross-section Tapered, with a head rounded ends
Semicircular
Application
General-purpose
power transmission
Heavy-duty, easy
disassembly
Machine tools,
alignment
Tapered shafts,
precise alignment
Torque Capacity
Moderate
High
Moderate
Moderate
Ease of Removal
Moderate
Easy (gib head)
Moderate
Moderate
Moderate
Reduced
Reduced
Semicircular keyway in
rectangular keyway shaft, rectangular in
with rounded corners hub
Stress Concentration Can be high
Flat Gib-Head Key
Pratt and Whitney
Key
Woodruff Key
Keyway
Square keyway
tapered keyway
Pros
simple to
manufacture, strong
connection
Easy removal, secure Reduced stress, aids Self-aligning, reduces
fit
alignment
stress
Cons
Can create stress
concentrations
More complex to
manufacture
less common than
other types
Deep keyway can
weaken shaft
7
Keys, Splines and Serrations
Dimensioning of Keyseats
▪ keyseats and keyways are dimensioned by
width, depth, location, if needed by length
▪ The depth is dimensioned from the opposite
side of the shaft or hole
Tapered Keyseats
▪ The depth of tapered keyways in hubs, which is shown on the drawing, is the nominal depth H/2
minus an allowance. This is always the depth at the large end of the tapered keyseat and is indicated
on the drawing by the abbreviation LE (Large End).
8
Splines
A series of ridges or teeth on a shaft that mesh with corresponding
grooves in a mating part, such as a hub or gear.
• Splines are used to transmit torque between a shaft and a rotating
component.
• They provide a more robust and reliable connection than a traditional key
and keyway, especially in high-torque applications.
• Unlike a single key, splines distribute the load over a larger surface area,
reducing stress concentration.
• Splines can also allow for axial movement of the mating part along the shaft,
while still transmitting torque.
• In essence, splines function as multiple keys formed integrally with the shaft.
• This design offers increased strength and durability compared to single-key
systems.
9
Splines - Types
•Involute Splines:
•These have teeth with an involute curve, similar to involute gears.
•They offer excellent load-carrying capacity and are widely used in high-torque applications.
•The involute form helps distribute the load evenly.
•Parallel Splines (Straight-Sided Splines):
•These have straight-sided teeth that are parallel to the shaft axis.
•They are simpler to manufacture than involute splines.
•They are used in various applications, including those requiring axial movement.
•Serrated Splines:
•These have V-shaped teeth.
•They are often used in smaller diameter shafts.
•They can provide a large number of teeth for precise positioning.
10
Keys, Splines and
Serrations
Drawing Data
▪ It is essential that a
uniform system of
drawing and specifying
splines and serrations
be used on drawings
▪ Involute spline:
▪ Spline type, fit, PD,
N, pitch.
▪ Straight –sided teeth:
▪ Type, Standard, N.
11
Drawing Considerations for Splines
Spline Type and Standard:
• Specify the Spline Type: Clearly indicate whether it's an involute, parallel, serrated, or other type.
• Reference Standards: Adhere to relevant industry standards (e.g., ANSI, ISO, DIN). This ensures
interchangeability and proper manufacturing. State the standard used on the drawing.
• Internal vs. External: Clearly differentiate between internal and external splines.
Dimensional Accuracy:
• Tooth Dimensions:
•
•
Specify the number of teeth, pitch, pressure angle (for involute splines), tooth depth, and tooth width.
Use appropriate tolerances for these dimensions.
• Major and Minor Diameters: Clearly dimension the major and minor diameters of both the shaft and
the hub.
• Form Diameter: For involute splines, this is very important.
• Length: Specify the length of the spline engagement.
• Tolerances: Apply appropriate tolerances to all dimensions to ensure proper fit and function.
12
Pin Fasteners
Machine pins serve a variety of crucial functions in mechanical systems, primarily related to:
•Alignment:
•Dowel pins, for example, are widely used to ensure precise alignment between two or more parts during
assembly. This is vital in applications requiring high accuracy, such as tool and die making.
•Fastening:
•Pins can securely fasten components together, preventing them from moving or separating. Taper pins,
for instance, create a tight, reliable connection.
•Creating Pivot Points:
•Clevis pins are specifically designed to create pivot points or hinged connections, allowing for controlled
movement between components.
•Securing Other Fasteners:
•Cotter pins are used to lock other fasteners, such as nuts or clevis pins, in place, preventing them from
loosening due to vibration or other forces.
•Positioning:
•Pins are utilised to accurately position parts, this is very important in manufacturing, and assembly
processes.
13
Cotter Pins:
•Function:
•Primarily used to secure other fasteners, preventing them from loosening.
•They are often used to lock castle nuts or clevis pins in place.
•Design:
•Made of soft wire with a split end.
•The prongs are bent outward after insertion to secure the pin.
•Applications:
•Automotive applications (securing wheel bearings, etc.).
•Machinery and equipment where vibration is a concern.
Dowel Pins:
•Function:
•Used for precise alignment of machine parts.
•They ensure accurate positioning during assembly.
•They can also resist shear forces.
•Design:
•Solid, cylindrical pins with tight tolerances.
•Typically made of hardened steel.
•Applications:
•Tool and die making.
•Precision machinery assembly.
•Jigs and fixtures.
Lynch Pins:
•Function:
•Designed for quick-release fastening.
•They are used to secure components that require frequent assembly and disassembly.
•Design:
•Typically have a looped or spring-loaded mechanism for easy insertion and removal.
•Often feature a self-locking design.
•Applications:
•Agricultural equipment (attaching implements).
•Trailers and towing applications.
•Any application requiring quick and easy fastening.
14
Spring Pins (also known as Roll Pins):
•Function:
•Primarily used for fastening and retaining components.
•Their spring-like action allows them to compress during insertion and then expand, creating a secure hold.
•Design:
•Hollow, cylindrical pins with a longitudinal slot.
•Made of spring steel, providing flexibility.
•They rely on their inherent spring force to maintain their position.
•Applications:
•Securing gears, levers, and other components.
•Used in applications where some flexibility is needed.
Detent Pins:
•Function:
•Used for quick-release fastening and positioning.
•They provide a means of temporarily locking components in place.
•Design:
•Typically feature a spring-loaded ball or plunger that engages with a mating hole or recess.
•Can have various release mechanisms, such as push buttons or pull rings.
•Applications:
•Adjustable equipment, such as exercise machines or material handling systems.
•Quick-release mechanisms in machinery.
Taper Pins:
•Function:
•Used for precise alignment and secure fastening.
•The tapered design ensures a tight, vibration-resistant fit.
•Design:
•Conical pins with a gradual taper.
•Driven into a matching tapered hole.
•Provide a very strong and accurate connection.
•Applications:
•Machine tools, jigs, and fixtures.
•Applications requiring high precision and resistance to loosening.
15
Pin Type
Primary Function Design
Material
Dowel Pin
Precise alignment Solid, cylindrical
Alignment and
secure fastening Tapered cylinder
Hardened steel
Taper Pin
Steel
Cotter Pin
Pivot point, hinged Cylindrical with
connections
head and hole
Securing other
Split wire with
fasteners
bent prongs
Lynch Pin
Quick-release
fastening
Looped or springloaded
Steel
Spring Pin (Roll
Pin)
Flexible fastening
and retaining
Slotted, hollow
cylinder
Detent Pin
Quick-release
positioning
Spring-loaded ball
or plunger
Steel
Clevis Pin
Steel
Soft metal (steel,
brass)
Spring steel
Key Applications Key Characteristics
Tool and die
making, machinery High accuracy, tight
assembly
tolerances
Machine tools,
Secure tapered fit,
jigs, fixtures
vibration resistance
Levers, linkages, Creates pivot
agricultural
points, uses cotter
equipment
pin
Securing clevis
Prevents loosening,
pins, castle nuts simple locking
Quick
Agricultural
insertion/removal,
equipment, trailers self-locking
Flexible, uses
Gears, levers,
spring force to
general fastening retain.
Adjustable
equipment, quickrelease
Provides quick
mechanisms
release locking.
16
Pin Fasteners – Grooved Pin Applications
17
Pin Fasteners – Spring Pin Applications
18
Pin Fasteners – Quick Release Pin
Applications
19
Retaining Rings
•Retaining rings are designed to hold components onto a shaft or within a housing or bore.
•They provide a shoulder that prevents axial movement of the retained components.
•They offer a cost-effective and efficient alternative to other fastening methods, such as threaded fasteners.
Material: Typically made from spring steel, carbon steel, or stainless steel, depending on the application's requirements for strength,
corrosion resistance, and temperature tolerance.
Installation:
•They are generally installed into grooves machined onto shafts or within housings.
•Specialized pliers or tools are often used for installation and removal.
Common Types
•Circlips: Tapered section rings providing secure retention.
•E-clips: Radial rings used for quick assembly.
•Snap rings: Constant section rings.
•Spiral retaining rings: Coiled rings providing 360° retention.
Advantages:
•Space-saving: They offer a compact design compared to other fastening methods.
•Cost-effective: They can reduce manufacturing and assembly costs.
•Reliability: They provide a secure and reliable means of retaining components.
•Ease of installation: many types are made for rapid assembly.
20
Retaining
Rings
21
Classified into 3 general groups
Controlled action Springs – have well defined function and constant range of action. Used in Valves and die
2.
Variable action Springs – have changing ranges due to various conditions. Used in Suspension, clutch and
cushion springs
3.
Static Springs – exert constant pressure or tension between parts. Used in packing or bearing pressure,
antirattle and seal springs
Springs
1.
22
Springs
Type of spring is determined by the characteristics such as function, shape of material,
application or design
Spring nomenclature, important parameters shown in 11-4-2
23
Variable action Springs
Have two distinct RATES, the
passing of one to the other
is carried out progressively
Have variations throughout
their construction
24
Common Spring Types
1. Helical Springs:
•Compression Springs:
•These are designed to resist compressive forces.
•They are commonly found in shock absorbers, valve
assemblies, and push-button mechanisms.
•Extension Springs (Tension Springs):
•These are designed to resist tensile forces.
•They are used in garage door mechanisms, trampolines,
and weighing scales.
•Torsion Springs:
•These are designed to resist twisting forces (torque).
•They are used in clothespins, hinges, and torsion bars in
vehicle suspensions.
25
Common Spring Types
2. Leaf Springs:
•These consist of multiple layers of flat metal strips (leaves) stacked together.
•They are primarily used in vehicle suspensions, especially in trucks and heavyduty vehicles, to absorb shock and distribute load.
3. Disc Springs (Belleville Springs):
•These are conically shaped washers that provide a high spring force in a small
space.
•They are used in applications requiring high loads and limited space, such as
valves, clutches, and heavy machinery.
4. Constant Force Springs:
•These springs provide a nearly constant force throughout their deflection
range.
•They are often used in applications requiring a consistent force, such as
retractable tape measures and clock mechanisms.
26
Compression Springs
Plain Open Ends: are produced by straight cutoff with no reduction of helix
angle
Needs bore or rod for guidance
Ground Open Ends: by parallel grinding of open end coil spring.
Improved stability & larger number of total coils
Plain Closed Ends: straight cutoff & Reduction of helix angle, more stable
Ground closed Ends: Parallel grinding of closed-end coil, more stability
27
Springs
▪ Extension Springs – are closed coiled helical spring that
offers resistance to pulling force
▪ Common end styles are shown in figure 11-4-3-b
▪ The end of the extension spring is the most stressed part
▪ Proper consideration should be given for selection of end style
▪ Different types of ends can be used on the same type of spring
28
Torsion Springs
▪ Torsion Springs – exerts pressure along a path that is a circular arc,
i.e. providing torque or torsion (example motor springs, power
springs etc.)
▪ It is a helical springs of round, square, or rectangular wire (strength).
▪ Few of the most common end styles are shown in figure 11-4-3-c
29
Spring Dimensioning
▪ Following information is given while dimensioning springs
in drawing (11-4- 8)
▪ Size, shape and material used in spring
▪ Dia (inside or outside)
▪ Pitch or No of coils
▪ Shape of ends
▪ Length
▪ Load and rate
▪ If schematic is used, of the wire to be stated
▪ Example – ONE HELICAL TENSION SPRING 3.00 LG (OR NUMBER OF COILS), 0.5 ID, PITCH .25, 18 B & S GA
SPRING BRASS WIRE
30
Rivets
▪ Riveting is a popular method of joining due to its simplicity,
dependability and low cost
▪ Rivets are permanent fasteners (unlike bolts and screws)
▪ A rivet is a ductile metal pin that is inserted through holes in two or more
parts, and having the ends formed over to securely hold the parts
▪ Rivets can be used to join dissimilar materials of various thicknesses
▪ Can serve as fasteners, pivot shafts, spacers or inserts
▪ Can be used to fasten finished parts (after plating painting etc)
▪If for maintenance, they have to be knocked out and clinched with new
rivets once again for assembly
▪They are neither watertight or airtight. But at higher cost they can be
made to with addition of sealing compound
31
Types of Riveted Joints
32
Large Rivets
▪ Used in structural work (buildings, bridges etc)
▪ Rivets have been replaced by high strength bolts
due to strength, cost and most importantly noise
factor
▪ Rivet joints are either Butt or Lap joints as seen
before
▪ Common types of large rivets are shown in 115-2
33
33
Large Rivets
▪ When shop rivets (which are put in the structure at the shop) are drawn, the diameter of the rivet head
is shown on the drawings. For field rivets, the shaft diameter is used
▪ Figure 11-5-3 shows the conventional rivet symbols adopted by the American and Canadian Institutes
of Steel Construction
34
Rivets for
Aersoapce
35
Rivets
Symbolic Representation of a Line of Rivets
▪ The crosses are aligned along the axes of drawing and number of places for rives indicated. If
supplemental info cannot be indicated on the drawing, use of leader lines to indicate them is fine
▪ When the rivets are aligned, identical, and equidistant, the symbols should be shown in the first and last
positions, together with the total number of pitches and distance (Fig. 11-5-5B)
36
Small Rivet Design Recommendations
Rivet Diameters - The optimum rivet diameter is determined, not by performance
requirements, but by economics-the costs of the rivet and the labor to install it. The rivet
length to-diameter ratio should not exceed 6:1
Rivet Positioning - The location of the rivet in the assembled product influences both joint
strength and clinching requirements. The important dimensions are edge distance and pitch
distance
Edge distance - Is the interval between the edge of the part and the center line of the rivet.
The recommended edge distance for plastic materials, either solid or laminated, is between
two and three diameters ( depending on the thickness and inherent strength of the material)
Pitch distance - Unnecessarily high stress concentrations in the riveted material and buckling
at adjacent empty holes can result if the pitch distance is less than three times the diameter of
the largest rivet in the assembly (metal parts) or five times the diameter (plastic parts)
37
Rivets
DESIGN
RECOMMENDATIONS
38
Blind Rivets
▪ Used when reverse side of the joint is not accessible. Sometimes they can be
used if other side is accessible as well
▪ Classified according to the methods to which they are set. Mainly pull mandrel,
drive pin and chemically expanded
39
Rivet Design
Considerations
40
The most common welded fasteners are screws and nuts. Here they are
grouped into Resistance welded fasteners and arc- welded studs
Welded
Fasteners
Resistance-Welded Fasteners
▪
An externally or internally threaded metal part designed to be fused
permanently in place by standard production welding equipment.
Methods of resistance welding:
▪
Projection welding
▪
Spot welding
41
Welded
Fasteners –
ResistanceWelded
Fasteners
▪
Projection welding - Heat is localized through embossed or coined
projections on the fastener. During the welding process, the projections
coalesce with the part surface to form the weld. For best results, a presstype welder with electronic controls is usually recommended. This type
of welder gives positive electrode alignment and equalized welding
pressures
▪
Spot welding - The current is directed through the entire area under the
electrode tip. Welding is usually performed by a spot welder. This type
of welding equipment can satisfactorily weld a number of fastener
designs
▪
Comparison - Spot welding costs less than projection welding. However,
the projection welder is more flexible and permits far greater latitude in
design
42
Welded Fasteners
43
44
Adhesive Fastening
To allow greater flexibility in design, styling and materials; and cost reduction adhesive fastening is
used. As with other methods these have their own advantages and disadvantages. For selection table
51 in appendix gives the application data
Adhesion Versus Stress
▪ Adhesion holds materials together and stress pulls them apart
▪ Tensile – pull equally over entire joint. All adhesive contribute to bond strength
▪ Shear – direction across the bond. Bond material slide over one another
▪ Peel – one of the surfaces is flexible and stress is concentrated on the thin line at the edge of the
bond
▪ Cleavage – Concentrated on one edge and the
other edge has zero stress
45
Adhesive Fastening
Advantages
▪
Resistance to stress is the reason for using adhesive fastening
▪
Adhesives allow uniform distribution of stress over the entire
bond area
1.
(Fig. 11-7-1). This eliminates stress concentration caused by rivets, bolts, spot welds, and similar fastening techniques.
Lighter, thinner materials can be used without sacrificing strength.
2.
Adhesives can effectively bond dissimilar materials.
3.
Continuous contact between mating surfaces effectively bonds and seals against many environmental conditions.
4.
Adhesives eliminate holes needed for mechanical fasteners and surface marks resulting from spot welding, brazing
46
Adhesive Fastening
Limitations
1. Adhesive bonding can be slow or require critical processing. This is particularly true in mass
production. Some adhesives require heat and pressure or special jigs and fixtures to
establish the bond
2. Adhesives are sensitive to surface conditions. Special surface preparation may be
required
3. Some adhesive solvents present hazards. Special ventilation may be required to protect
employees from toxic vapors
4. Environmental conditions can reduce bond strength of some adhesives. Some do not hold
well when exposed to low temperatures, high humidity, severe heat, chemicals, water
47
Adhesive
Fastening
Joint Design
▪
Joints need to be specifically
designed
▪
All the bonded area share
the load equally
▪
Joint configuration should be
designed so that basic stress
is primarily in shear or
tensile
▪Cleavage and peel to be minimized
or eliminated
48
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Joint Design
▪ Angle Joints – give rise to peel or cleavage stress depending on the
gage of metal. To reduce cleavage, typical approaches are shown
▪ Butt Joints – illustrated recessed butt joints are recommended
▪ Cylindrical Joints – the T joint and overlap slip joint are typical for
bonding cylindrical parts such as tubing, bushings and shafts
49
Adhesive Fastening
Joint Design
▪ Corner Joints – sheet metal – assembled with adhesives using supplementary
attachments. This permits joining and sealing in one operation. Typical joints are
▪ Corner Joints – rigid members – as in decorative fames can be adhesively
bonded. End lap joints are simplest, they require machining. Mortise and
tenon joints are excellent from design point, and require machining. Mittered
joints are good if both members are hollow extrusions
▪ Stiffener Joints – deflection and flutter of thin metal sheets can be minimized
with adhesive bonded stiffeners
50