Shafts Flashcards
What is a component of all mechanical devices that transmits motion and power called?
Shaft
A rotating device on which a wheel is mounted is called what?
Axle
A slender pin or rod which turns or on which something else turns
Spindle
How are axles loaded?
Transversely
What defect are axles most susceptible to?
Bending
What are spindles commonly used for?
Carrying a tool for doing work
What is the part of the spindle, shaft, or axle that rotates on a bearing called?
Journal
What are the 4 main categories of shafting finishes?
Hot rolled
Cold rolled
Ground
Plated
How is shaft selection determined ? (6)
-torque
-speed
-components and their mounting
-compression and tensile limits
-cost
-contraction, bowing, or expansion limitations (distance between supports)
Describe what a hot rolled shaft looks like
Dark surface
Rough
Oxidized finish
Cold rolling, machining, centreless grinding, grinding and polishing, and chrome playing are all examples of what?
Finished shafting
Describe what a finished shaft looks like
Smooth finish
Close tolerances
What are the two most common types of carbon steel finished shafting called?
ASIS C1018
ASIS C1045/C1050
Describe AISI C1018 shafting
Cold finished steel
Low carbon range
Welds readily
Smooth finish
What is AISI C1018 commonly used for?
General shafting purposes
Spindles
Pins
What should AISI C1018 NOT be used for?
Applications involving high speed or high stress
What are a few characteristics of C1018 shafting
Bright smooth surface
Easily machined
Low cost
Minus tolerance (under sized)
Describe AISI C1045/C1050 shafting
Known as precision shafting
Medium carbon steel
High strength
Distortion free
Can be used with high speeds
What are some other ways C1045/C1050 shafting can be offered?
Chrome plated finish
(Hydraulic piston rods and shafts)
When would Alloy shafting be used?
Where wear and corrosion are a concern
What are the 4 main types of alloy shafting available?
Chrome alloys (stainless steel)
High magnesium alloys
Nickel chrome steel alloy
Brass/bronze
What are the benefits of chrome alloy shafting?
Hard
Wear resistant
Corrosion resistant
What are the benefits of high magnesium alloy shafting?
Long durability
What are the benefits of nickel chrome steel alloy shafting?
High inherent strength
What are the benefits of brass/bronze shafting?
Tough
Corrosion resistant
Wear resistant
Where are both high magnesium and nickel chrome steel alloy shafts commonly used?
Crankshafts
What is AISI 4140 shafting?
Chrome molybdenum steel alloy
What are the characteristics of 4140 shafting?
General purpose
Medium carbon
High strength
Very ductile
Where is 4140 shafting generally used?
Gears
Axles
And shafts
Where is hollow shafting commonly used?
Power transmissions
Is hollow shafts worth the strength loss?
Normally yes. The weight loss is significantly greater than the strength lost
What are examples of what shafts are used for?
-transfer torque
-Support equipment
-pivot point
-allow for a sliding action
-change rotation
How can you properly identify shafting
Visually
Physically
What are some visual ways to identify shafting?
Surface colour
Finish
Weight
Magnetic properties
What are some physical ways to identify a shaft?
Spark test
Hammer and chisel test
File test
Is colour coding reliable for identifying shafts?
No
Define tensile shaft stress
Stress that lengthens or stretches the shaft
Define compressive shaft stress
Stresses that compress or shorten the shaft
Define bending shaft stress
A combination of tensile and compressive stress
Define shear stress in a shaft
When the applied force tends to cut through the shaft
How would you check runout in a shaft?
Use a dial indicator while rotating the shaft
What is the greatest danger when straightening shafts in a press?
The shaft rolling or springing away
What tests could you do in the shop to determine a type of shafting?
Colour
Density
Chip
Magnetic
Spark
What is the best way to identify shafting material?
Good house keeping
What is the difference between hot rolled and cold rolled steel?
Surface finish
Size tolerance
What are the sources of stress on a shaft?
- shaft weight
- components on the shaft
- location of bearings
Define shaft fatigue loading
When the shaft is subject to many cycles of loading, stresses encountered are called fatigue loading
Define shaft fatigue strength
The ability to resist fatigue
What causes cycle loading (shafts)
Produced when a load applied to the shaft bends it then rotated and the bending continues
What is a shoulder on a shaft?
A change in diameter occurs in a shaft
What are the 3 main ways to reduce stress on a shaft?
Maintains surface finish
Keys with broken edges
When turning down a shaft keep the ratio to good proportions
What does edges broken in terms of keys refer to?
Sharp corners removed
When turning down a shaft what ratio should be maintained?
1.5:1
Define bending stress
Combination of tensile and compressive stresses
Define shear stress
Occurs when the applied force tends to cut through
What is tensile stress?
If the stress tends to stretch or lengthen the shaft
What is compressive stress?
If the stress tends to compress or shorten the shaft
What is torsional shear stress?
Twisting causing a shear stress in the shaft in a non uniform way
What is torsional deformation?
Twisting causing shear stress in the shaft
Can failure to locate bearings correctly change clearance of parts? (Y/N)
Yes
What factors should be attended to in order to keep shafts in good working order? (4)
Alignment
Shaft centres
Critical speed
Runout
If you have precise alignment what negative affects can be reduced? (3)
Wear
Vibration
Fatigue loading
What does alignment refer to?
The axis of shafts being parallel and in line NOT offset
“The axis of shafts being parallel and in line NOT offset” is what?
Alignment
As speed on a shaft increases a point is eventually reached where there is excessive vibration. The speed at which this vibration occurs is called what?
Critical speed
What does critical speed depend on? (4)
Size of load
Length of shaft
Diameter of shaft
The type of support bearings
Typically how far under the critical speed is a machine set?
20% under
How many types of runout is there?
3
What is runout?
Any deviation/wobble from true
What is radial runout?
When the shaft and the attachments are not centric in rotation
Why does circular runout occur?
Due to the imperfections (bumps) in the cross section of the part
When does axial runout occur?
When attachments do NOT rotate perpendicularly to the shaft axis
What can cause runout on a shaft? (4)
Bent shaft
Worn bearings
Poor machining
Poor assembly
What can be the result of excessive runout? (3)
Vibration
Wear
Seizing
What are the two main methods for checking for runout?
Shaft between centres
Dial indicator
How do you confirm the cause for run out with a dial indicator and a micrometer?
By comparing the circular runout to the radial
What are the two methods for repairing a damaged shaft?
Metalizing
Sleeves
What is metalizing a shaft?
A technique of spraying metal coating onto a shaft
What is sleeving a shaft?
Placing a sleeve (machined metal “bushing”) with an interference fit onto a shaft
What are the two common methods for repairing a bent shaft?
Hydraulic Press
Heat
What must you consider when selecting a shaft material?
Weight
Strength
Magnetic qualities
Shock resistance
Expansion
Corrosion
What are the two main stress that affect a shaft?
Bending stress
Torsional stress
Define bending stress
The force applied by the weight of the shafting loads perpendicular to the shaft axis between bearings
How can you keep bending stresses to a minimal?
Keep loads close to the bearings
Define torsional stress
The force applied to the shaft by the resistance to turning that is set by the driven parts
What is the 4 most common shapes for shafting?
Solid round
Square
Hex
Hallow
Other than reducing weight what is the benefit of hollow shafting?
Conduct coolant
What is line shafting?
Supplies power or timing to several drives on a single shaft
What is the maximum distance between bearings on a line shaft?
8 feet
Where should gears, pulleys, and sprockets be on a shaft?
As close to the bearings as possible
Where should the fix bearing on a shaft be located?
As close to the main drive sprocket, pulley, or gear as possible
What type of bearing housing should you use on a line shaft?
Pillow block
Why are alloys added to shafting material?
To improve their qualities
What qualities can be improved in shafting with the use of alloys? (4)
Hardness
Abrasion resistance
Corrosion
Machinability
What is the benefits of using a aluminum alloy in shafting? (2)
Controls grain size
Case hardens
What is the benefit of using a carbon alloy in shafting material? (1)
Higher hardness
What is the disadvantages to using a higher carbon alloy in steel?
Lower ductility
Lower weld ability
What is the principal element in steel?
Carbon
What is the benefit of using a higher chromium alloy in shafting material? (3)
Improves
Hardenability
Abrasion resistance
Wear resistance
What applications can chromium be added to shafting for?
Higher temperature applications
What is the benefit of using a higher copper alloy in shafting material? (1)
Improves corrosion resistance
At what percentage does copper not significantly affect a shafts mechanical properties?
Less than 1%
For most carbon and alloy steels the AISI and SAE systems use a 4 digit designation. What does the last 2 digits refer to?
Indicate the amount of carbon content
For most carbon and alloy steels the AISI and SAE systems use a 4 digit designation. What does the FIRST 2 digits refer to?
Indicate the specific alloy group
What does fit express?
The range of permissible tightness or looseness
What is the typical cause for spalling?
Fatigue failure
