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Parents Pricing Home NSC Mechanical Technology Fitting and Machining Basic calculations on forces, moments and stress and strain 5.1 A parallel key must be machined to fit onto an 84 mm diameter shaft
5.1 A parallel key must be machined to fit onto an 84 mm diameter shaft - NSC Mechanical Technology Fitting and Machining - Question 5 - 2018 - Paper 1 Question 5
View full question 5.1 A parallel key must be machined to fit onto an 84 mm diameter shaft. Calculate the following:
5.1.1 The width of the key
5.1.2 The thickness of the key
5.1.3 Th... show full transcript
View marking scheme Worked Solution & Example Answer:5.1 A parallel key must be machined to fit onto an 84 mm diameter shaft - NSC Mechanical Technology Fitting and Machining - Question 5 - 2018 - Paper 1
5.1.1 The width of the key Only available for registered users.
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To find the width of the key, divide the diameter of the shaft by 4:
ext{Width} = rac{D}{4} = rac{84 ext{ mm}}{4} = 21 ext{ mm}
5.1.2 The thickness of the key Only available for registered users.
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The thickness of the key is calculated using the formula:
ext{Thickness} = rac{D}{6} = rac{84 ext{ mm}}{6} = 14 ext{ mm}
5.1.3 The length of the key Only available for registered users.
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The length of the key can be calculated as:
e x t L e n g t h = D i m e s 1.5 = 84 e x t m m i m e s 1.5 = 126 e x t m m ext{Length} = D imes 1.5 = 84 ext{ mm} imes 1.5 = 126 ext{ mm} e x t L e n g t h = D im es 1.5 = 84 e x t mm im es 1.5 = 126 e x t mm
5.2 Simple indexing for spur gear Only available for registered users.
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Simple indexing can be calculated as:
ext{Indexing} = rac{40}{n} = rac{40}{2} = 20 ext{ holes per full turn}
No full turns and 20 holes on the 53-hole circle will be used.
5.3 Depth of the screw thread Only available for registered users.
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The depth of the thread is given by:
e x t D e p t h = 0.866 P = 0.866 i m e s 2 e x t m m = 1.732 e x t m m ext{Depth} = 0.866P = 0.866 imes 2 ext{ mm} = 1.732 ext{ mm} e x t De pt h = 0.866 P = 0.866 im es 2 e x t mm = 1.732 e x t mm
5.4.1 Addendum Only available for registered users.
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The addendum is equal to the module:
e x t A d d e n d u m = m = 3 e x t m m ext{Addendum} = m = 3 ext{ mm} e x t A dd e n d u m = m = 3 e x t mm
5.4.2 Dedendum Only available for registered users.
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The dedendum is calculated as:
e x t D e d e n d u m = 1.157 m = 1.157 i m e s 3 e x t m m = 3.471 e x t m m ext{Dedendum} = 1.157 m = 1.157 imes 3 ext{ mm} = 3.471 ext{ mm} e x t De d e n d u m = 1.157 m = 1.157 im es 3 e x t mm = 3.471 e x t mm
5.4.3 Clearance Only available for registered users.
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The clearance can be determined using:
e x t C l e a r a n c e = 0.157 m = 0.157 i m e s 3 e x t m m = 0.471 e x t m m ext{Clearance} = 0.157 m = 0.157 imes 3 ext{ mm} = 0.471 ext{ mm} e x t Cl e a r an ce = 0.157 m = 0.157 im es 3 e x t mm = 0.471 e x t mm
5.4.4 Pitch-circle diameter (PCD) Only available for registered users.
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The pitch-circle diameter is calculated as:
e x t P C D = m i m e s T = 3 i m e s 48 = 144 e x t m m ext{PCD} = m imes T = 3 imes 48 = 144 ext{ mm} e x t PC D = mim es T = 3 im es 48 = 144 e x t mm
5.4.5 Outside diameter Only available for registered users.
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The outside diameter is obtained using:
e x t O D = P C D + 2 m = 144 + 2 ( 3 ) = 150 e x t m m ext{OD} = PCD + 2m = 144 + 2(3) = 150 ext{ mm} e x t O D = PC D + 2 m = 144 + 2 ( 3 ) = 150 e x t mm
5.4.6 Cutting depth Only available for registered users.
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The cutting depth is:
e x t C u t t i n g d e p t h = 2.157 m = 2.157 i m e s 3 e x t m m = 6.471 e x t m m ext{Cutting depth} = 2.157 m = 2.157 imes 3 ext{ mm} = 6.471 ext{ mm} e x t C u tt in g d e pt h = 2.157 m = 2.157 im es 3 e x t mm = 6.471 e x t mm
5.4.7 Circular pitch Only available for registered users.
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The circular pitch is calculated as:
ext{Circular pitch} = m imes rac{3.14}{180} ext{ Deg} = 3 ext{ mm}
5.5 Identify the type of key shown in FIGURE 5.5 Only available for registered users.
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The type of key shown in FIGURE 5.5 is a parallel key, Pratt and Whitney key, or feather key.
5.6 Identify the milling process shown in FIGURE 5.6 Only available for registered users.
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The milling process shown in FIGURE 5.6 is straddle milling.
5.7 Identify the engineering equipment shown in FIGURE 5.7 Only available for registered users.
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The engineering equipment shown in FIGURE 5.7 is a milling machine, which can be a universal, vertical, or horizontal milling machine.
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