Shafts Flashcards by Krista Jarvis

What is a component of all mechanical devices that transmits motion and power called?

Shaft

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A rotating device on which a wheel is mounted is called what?

Axle

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A slender pin or rod which turns or on which something else turns

Spindle

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How are axles loaded?

Transversely

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What defect are axles most susceptible to?

Bending

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What are spindles commonly used for?

Carrying a tool for doing work

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What is the part of the spindle, shaft, or axle that rotates on a bearing called?

Journal

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What are the 4 main categories of shafting finishes?

Hot rolled
Cold rolled
Ground
Plated

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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)

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Describe what a hot rolled shaft looks like

Dark surface
Rough
Oxidized finish

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Cold rolling, machining, centreless grinding, grinding and polishing, and chrome playing are all examples of what?

Finished shafting

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Describe what a finished shaft looks like

Smooth finish
Close tolerances

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What are the two most common types of carbon steel finished shafting called?

ASIS C1018
ASIS C1045/C1050

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Describe AISI C1018 shafting

Cold finished steel
Low carbon range
Welds readily
Smooth finish

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What is AISI C1018 commonly used for?

General shafting purposes
Spindles
Pins

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What should AISI C1018 NOT be used for?

Applications involving high speed or high stress

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What are a few characteristics of C1018 shafting

Bright smooth surface
Easily machined
Low cost
Minus tolerance (under sized)

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Describe AISI C1045/C1050 shafting

Known as precision shafting
Medium carbon steel
High strength
Distortion free
Can be used with high speeds

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What are some other ways C1045/C1050 shafting can be offered?

Chrome plated finish
(Hydraulic piston rods and shafts)

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When would Alloy shafting be used?

Where wear and corrosion are a concern

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What are the 4 main types of alloy shafting available?

Chrome alloys (stainless steel)
High magnesium alloys
Nickel chrome steel alloy
Brass/bronze

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What are the benefits of chrome alloy shafting?

Hard
Wear resistant
Corrosion resistant

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What are the benefits of high magnesium alloy shafting?

Long durability

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What are the benefits of nickel chrome steel alloy shafting?

High inherent strength

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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?

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?

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