7.6 Fits And Clearances Flashcards

1
Q

What’s the high limit

A

The largest acceptable size for a particular dimension

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2
Q

What are the two types of clearance fit

A

Running and free running

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3
Q

What two subsections can transition fits be divided into

A

Push and light press

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4
Q

What’s an interference fit

A

Where the hole is smaller than the item being fitted

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5
Q

What subsections are interference fits split up into

A

Drive , press, force

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6
Q

What’s a shrink fit

A

Extreme type of interference fit and is where the shaft is much larger than the whole so is achieved by heating the outer part so it expands

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7
Q

What is known as a good fit?

A

Josh Willy + Sean/Lewis bums

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8
Q

How does wear occur?

A

When there is motion between 2 parts (Willy and bum)

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9
Q

What are the limits for twists?

A

If released and it untwisted it is below elastic limit, if stays same shape is above elastic limit

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10
Q

What are the 4 dimensions for wear?

A

Dimensions new, clearance new, permissible worn dimensions, permissible worn clearance

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11
Q

What is a dial test indicator? (DTI)

A

Precision tool used to measure movement

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12
Q

How should clearance fit components be assembled?

A

Light hand pressure

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13
Q

How should interference fit components be assemble?

A

With force

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14
Q

What is the ISO system?

A

It between shafts and bearing

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15
Q

What’s a small limit

A

The smallest acceptable size for a certain dimension

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16
Q

What’s the difference between the high and the low limit

A

The tolerance

17
Q

What is the allowance

A

When two components are to be fitted together, the difference between the high limit of the inside component and the low limit of the surrounding component

18
Q

If a parts are intended to move together then what documentation must it have

A

Schedule of fits and clearances for the aircraft

19
Q

What characteristics does the schedule or fits and clearances intail

A

Ovality
Bow of shaft
Twist of shaft

20
Q

What does it mean if an item is bowed

A

The centre line of the item is not straight

21
Q

How do you measure the amount of twist an object is under while in operation

A

By using a Strain gauge

22
Q

If the shaft remains twist after the load has been removed, it has been????

A

Loaded above it’s elastic limit

23
Q

What are the four dimensions for the limits of wear

A

Dimensions new
Permissible worm dimension
Clearance new
Permissible worn clearance

24
Q

What does dimensions new mean

A

Relates to size of part when it’s new and shows relevant dimensions

25
Q

What does permissible worn dimensions mean

A

The size which a part may wear too before it’s unserviceable

26
Q

What does clearance new mean

A

Desired clearance in limit form
(Interference fits are quoted as negative clearances)

27
Q

What does permissible worn clearance mean

A

The maximum allowable clearance when reassembling a component

28
Q

What are the two methods for checking shafts, bearings and other parts

A

Dial test indicator (DTI)
Checking method

29
Q

What is a DTI and what does it do

A

Dial test indicator
Precession measuring instrument that can be used to measure the amount of movement between certain engine and airframe parts

30
Q

What is a checking method (Dont think we will need to know)

A

Engine crankshaft runout is checked with a DTI by assembling the instrument onto a stand and positioning it onto a smooth part of the crankshaft, then adding a load to the DTI, pressing it u0 against the shaft so the pointer deflects a few thousands of an inch.
DTI is the zeroed, as crankshaft is turned, the DTI will indicate the amount of deviation in both directions