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Industrial Mechanic 2nd Block, Harmonized > Shaft Attachments and Fits > Flashcards

Shaft Attachments and Fits Flashcards

1
Q

In any mechanical arrangement the static and dynamic positions of the shafts are established and maintained by the:

A

Bearings

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2
Q

Any geometric or dimensional inaccuracy in the shaft may directly affect the performance of: (2)

A

Bearings and the machine

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3
Q

In the simple case of a shaft rotating under a radial load and being supported by two bearings, specific factors related to _____, _____ and _____ can affect the runout of the shaft

A

Shaft, Bearing components, and Housing

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4
Q

some of the conditions that influence shaft position are: (9)

A
  • Straightness
  • Roundness
  • Size or Fit with bearing
  • Bearing seat concentricity
  • Bearing seat squareness
  • Radius fillets at shoulders of shaft
  • Deflection of shaft
  • Means of retaining the bearing in position
  • Balancing
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5
Q

Almost all conditions that influence shaft position relate directly or indirectly to:

A

Bearing installation

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6
Q

the primary requirement for bearing shafting is that it be:

A

The proper size

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7
Q

dimensions must be accurate for both shaft _____ and _____ locations along the shaft.

A

shaft diameters and axial locations

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8
Q

Oversize shaft diameters invite: (2)

A

Overheating or Preloading

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9
Q

Undersize shaft diameters may contribute to: (3)

A
  • Fretting of the shaft
  • loosening of the bearing
  • excessive internal clearance
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10
Q

Another basic requirement is that a shaft has the correct surface finish. This finish is given in: (3)

A
  • Micrometres (µm) AA
  • Microinches (µin)
  • Root mean square (rms)

Note: AA refers to the arithmetical average height of surface roughness

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11
Q

Root mean square is considered the better method of determining surface finish as it emphasizes:

A

Extreme surface deviations

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12
Q

Shaft surface requirements depend on: (2)

A

Bearing materials and types

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13
Q

most anti-friction bearings require a surface finish of up to ___ µm AA

A

0.30 µm AA (12 µin)

Note: Too rough a surface finish may result in the loss of interference fit, excessive shaft wear, and fretting of the bearing seat

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14
Q

Babbit and bronze sleeve bearings require a finish of up to ___ µm AA

A

0.81 µm AA (32 µin)

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15
Q

The shafting should be straight and free of nicks, gouges, scratches or burrs. Imperfections can interfere with _____ _____ and cause _____ _____.

A

Bearing Lubrication and cause Localized Scoring

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16
Q

Retention of bearings on a shaft is influenced by these three things: (3)

A
  • Fit
  • Hardness/finish of material
  • deflection of the shaft
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17
Q

most anti-friction bearings are mounted on a shaft with a slight interference fit. Too loose a fit may cause the inner ring of the bearing to:

A

Creep on the shaft

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18
Q

Non-ferrous shaft materials require special attention. Why is this?

A

The thermal coefficient of expansion in ferrous vs non ferrous metals means the fit of a bearing on a shaft varies with temperature.

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19
Q

A hub is a machine element fitted to components such as gears, sheaves, or sprockets for the purpose of:

A

enabling a component to be attached to a shaft

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20
Q

Typically hubs are assembled to shafts prepared with a:

A

Keyseat

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21
Q

What are the steps to install a hub? (4)

A
  • Install the key into the shaft keyseat
  • Lubricate the shaft with with an oil or anti-seize
  • align the hub keyseat with the key
  • slide the hub into position
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22
Q

the method used to position a hub is dictated by: (3)

A
  • fit
  • type of equipment
  • style of hub
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23
Q

couplings are used to connect two shafts together at their ends for the purpose of:

A

Transmitting power

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24
Q

Name the two general types of couplings: (2)

A

Rigid and Flexible

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25
Q

Rigid couplings are designed to connect shafts together _____, making a single unit.

A

Rigidly

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26
Q

When installing a coupling, ensure the shaft is straight, free of rust, paint, dirt, burrs or imperfections. This is because they could alter:

A

Coupling position

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27
Q

For general purposes, a coupling should have a ________ fit to the shaft.

A

locational interference fit

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28
Q

The class of fit for a coupling is dictated by: (3)

A
  • Type of coupling
  • diameter of shaft
  • torque
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29
Q

flexible and rigid couplings have similar shaft requirements, however flexible couplings may use:

A

Other mounting methods

30
Q

What are three other mounting methods that flexible couplings may use? (3)

A
  • plain taper bushings
  • flanged taper bushings
  • tapered shaft and locknut

Note: In most cases a key is included in the connection

31
Q

Many machine components are attached to shafts for the purpose of transmitting torque. The means used for axial location depend heavily on whether or not:

A

axial thrust is transmitted

32
Q

v-belt sheaves, chain sprockets and spur gears produce ____ thrust loads.

A

small thrust loads

Note: many types of gears can produce varying amounts of thrust loads

33
Q

Gears can be keyed to a shaft, and then locked in place by any of the following methods: (9)

A
  • Interference fit
  • set screws
  • plain tapered bushing
  • flanged tapered bushing
  • locking collar and set screw
  • pinning
  • retaining rings
  • tapered shaft with key and locknut or screw
  • molding polymer
34
Q

in applications where a gear is required to slide on the shaft, such as in a gearbox, what methods could accomplish this? (3)

A
  • fixed feather key
  • sliding feather key
  • spline
35
Q

compression fittings are a method of:

A

attaching machine components to standard size shafting

Note: quick to install and dismantle

36
Q

in the simplest form, a hub on a sprocket can be slotted axially, and a clamp (bolt) drilled:

A

through the hub

Note: when the clamp is drawn tight, it forces the split hub into contact with the shaft. The pressure on the shaft allows the transmission of torque

37
Q

To maintain a sprockets relative position on a shaft, what is inserted?

A

a key

38
Q

maintaining concentricity of a component can be difficult with this type of connection:

A

Compression fitting

39
Q

the difficulties encountered with simple clamp compression fittings can be overcome by using a:

A

Plain tapered bushing

Note: the bushing has a small taper on its outer surface and the hub has a matching taper in its bore

40
Q

when a plain tapered bushing is pulled into a mating hub with a prescribed number of screws, it:

A

compresses tightly to the shaft.

41
Q

a ____ is used as a positive means of transmitting torque with a plain tapered bushing

A

key

42
Q

flanged, tapered bushings are a quick means of installing sprockets and sheaves to shafts. _____ is maintained with this.

A

Concentricity of the sheave

43
Q

like with a plain tapered bushing, the hub is machined with a taper in its bore to match the bushings taper. The components can be lightly assembled and then installed, secured it place by:

A

tightening the cap screws that compress the bushing in the hub tight to the shaft.

44
Q

a flanged tapered bushing is easily removed from its hub using:

A

the jackscrews in the holes tapped into the face of the sprocket

45
Q

A millwright often needs to make decisions regarding the fit of machine components. When doing so, sketches must be fully dimensioned and give the:

A

appropriate tolerances

46
Q

A tolerance is:

A

the total permissible deviation of a dimension on a part

it is the difference between the max and min limits on size

47
Q

when applying tolerances to dimensions of mating parts, what two systems may be used? (2)

A
  • basic hole system

- basic shaft system

48
Q

in this system of applying tolerances, the hole is the basic size, and the allowance is on the shaft. For example, when a replacement shaft is to be fitted with a standard anti friction bearing:

A

Basic hole system

49
Q

in this system of applying tolerances, the design size of the shaft is the basic size and allowance is left in the bore of the mating part. For example, when replacing a worn out sprocket on an existing shaft:

A

Basic shaft system

50
Q

Tolerance may be expressed as: (2)

A
  • Unilateral

- Bilateral

51
Q

Tolerance being applied in one direction only is known as:

ex: 4.500” +0.000 -0.002

A

Unilateral tolerance

52
Q

tolerance being applied in both directions is known as:

ex: 4.500” +0.002 -0.002

A

Bilateral Tolerance

53
Q

The terms allowance and fit are used interchangeably. Allowance is the:

A

prescribed difference between maximum material limits of mating parts (maximum interference)

54
Q

The terms allowance and fit are used interchangeably. Fit is:

A

determined by allowance. Allowance determines the fit between two mating parts

55
Q

positive allowance refers to:

A

minimum clearance between mating parts (clearance fit)

56
Q

negative allowance refers to:

A

maximum interference (interference fit)

57
Q

the degree of fit is a result of specifying a ____ to each mating part

A

tolerance

58
Q

two basic types of fit are: (2)

A

Clearance and interference fit

59
Q

This fit allows the mating parts to maintain some clearance between them at all times:

A

Clearance fit

60
Q

This fit maintains some resistance between mating parts at all times:

A

Interference fit

61
Q

This class of fit provides clearance between mating parts for lubrication. It applies mainly to rotating parts such as a shaft in a friction bearing. fit must not be so close that it cannot turn, but not so loose that it floats about:

A

Running fit

62
Q

this class of fit applies to parts which slide on each other, such as a dovetail slide.

A

Sliding clearance fit

63
Q

when using a dovetail slide with a gib, the gib:

A

is normally used to adjust clearance between mating parts.

64
Q

sliding clearance fits can be subdivided into these types of fit: (7)

A
  • Close sliding
  • sliding
  • precision
  • close running
  • medium running
  • free running
  • loose running
65
Q

These fits are intended for normally stationary parts which can be freely assembled or disassembled:

A

locational clearance fit

Note: various classes from snug to medium clearance fits satisfy the needs of various applications

66
Q

when the tolerance on the mating parts partially overlaps so that either a clearance or interference may result, the fit is called:

A

transition fit

Note: These fits are used to locate mating parts, such as a dowel pin and mating hole aligning machine parts.

67
Q

when accurate location and rigid alignment are of the utmost importance, what fit would you use?

A

locational interference fits

Ex: anti-friction bearing pressed into a housing

Note: Because of their tightness, it’s not recommended to use this fit to transfer frictional loads.

68
Q

when the tolerance of mating parts fully overlaps, causing an interference fit, the fit is classed as:

A

force or shrink fits

Note: This fit requires parts to be forced or shrunk together to ensure they act as one unit. Pressure deforms mating parts as they are assembled.

69
Q

If interference is excessive, the elastic limit of the material will be exceeded and assembled parts distorted. In extreme cases, the ultimate strength of the metal will be exceeded and:

A

the outer part will burst

70
Q

ensure that mating parts are within the _____ _____ for the designated fit

A

prescribed tolerances

Industrial Mechanic 2nd Block, Harmonized (28 decks)

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