5.1 A spur gear with 118 teeth must be cut on a universal milling machine. Calculate the indexing required to cut this gear with the help of a Cincinnati dividing head. 5.2 Use simple line sketches to explain the difference between up-cut milling and down-cut milling on a milling machine. Indicate the work-piece feed and cutter rotation. 5.3 A tapered gib-head key must be made to fit a 102 mm diameter shaft. Calculate the following key dimensions: 5.3.1 The width of the key: 5.3.2 The thickness of the key: 5.3.3 The length of the key: 5.3.4 The thickness of the key at the smaller end: 5.4 A spur gear has 60 teeth and a module of 3. Calculate the following in respect of the spur gear: 5.4.1 Addendum 5.4.2 Dedendum 5.4.3 Clearance 5.4.4 Pitch circle diameter 5.4.5 Outside diameter 5.4.6 Cutting depth 5.4.7 Circular pitch

NSC Mechanical Technology Automotive Calculations on drill and key sizes: 5.1 A spur gear with 118 teeth m

5.1 A spur gear with 118 teeth must be cut on a universal milling machine - NSC Mechanical Technology Automotive - Question 5 - 2017 - Paper 1

Question 5

5.1 A spur gear with 118 teeth must be cut on a universal milling machine. Calculate the indexing required to cut this gear with the help of a Cincinnati dividing he... show full transcript

Worked Solution & Example Answer:5.1 A spur gear with 118 teeth must be cut on a universal milling machine - NSC Mechanical Technology Automotive - Question 5 - 2017 - Paper 1

Step 1

5.1 A spur gear with 118 teeth must be cut on a universal milling machine. Calculate the indexing required to cut this gear with the help of a Cincinnati dividing head.

96%

114 rated

Answer

To calculate the indexing, we utilize the formula:

ext{Indexing} = \frac{40}{n}

Where:

n = number of divisions.
For 118 teeth, we set n as follows:

ext{Indexing} = \frac{40}{118} = 0.339 ext{ (approximately)}

The result means you can set up the dividing head for 40 / n divisions. We confirm the setup has no full turns with 20 holes in a 59-hole plate.

Step 2

5.2 Use simple line sketches to explain the difference between up-cut milling and down-cut milling on a milling machine. Indicate the work-piece feed and cutter rotation.

99%

104 rated

Answer

Up-cut Milling

The cutter rotates counterclockwise.
The work-piece feed moves against the direction of cutter rotation.
A sketch would show the cutter pulling the material up, resulting in a slightly smoother finish but creating a risk of chatter.

Down-cut Milling

The cutter rotates clockwise.
The work-piece feed moves in the same direction as the cutter rotation.
A sketch would show the cutter pushing the material down, providing a better surface finish but can cause more tool wear.

Step 3

5.3.1 The width of the key:

96%

101 rated

Answer

The width of the key can be calculated using:

ext{Width} = \frac{D}{4} = \frac{102}{4} = 25.5 ext{ mm}

Step 4

5.3.2 The thickness of the key:

98%

120 rated

Answer

The thickness of the key can be calculated using:

ext{Thickness} = \frac{D}{6} = \frac{102}{6} = 17 ext{ mm}

Step 5

5.3.3 The length of the key:

97%

117 rated

Answer

The length of the key is:

ext{Length} = D \times 1.5 = 102 \times 1.5 = 153 ext{ mm}

Step 6

5.3.4 The thickness of the key at the smaller end:

97%

121 rated

Answer

The thickness at the smaller end can be determined using:

ext{Thickness at smaller end} = T - \frac{L}{100} = 17 - \frac{153}{100} = 15.47 ext{ mm}

Step 7

5.4.1 Addendum

96%

114 rated

Answer

Addendum = m = 3 mm

Step 8

5.4.2 Dedendum

99%

104 rated

Answer

Dedendum can be calculated as:

ext{Dedendum} = 1.157 m = 1.157 \times 3 = 3.471 ext{ mm}

Step 9

5.4.3 Clearance

96%

101 rated

Answer

Clearance = 0.157 m = 0.157 \times 3 = 0.471 ext{ mm}

Step 10

5.4.4 Pitch circle diameter

98%

120 rated

Answer

Pitch circle diameter (PCD) can be calculated using:

\text{OD} = \text{PCD} + 2m = 180 + 2(3) = 186 ext{ mm}

Step 11

5.4.5 Outside diameter

97%

117 rated

Answer

Outside diameter can be calculated as:

\text{OD} = 180 + 2(3) = 186 ext{ mm}

Step 12

5.4.6 Cutting depth

97%

121 rated

Answer

The cutting depth is:

\text{Cutting depth} = 2.157 + 2.25 = 6.47 ext{ mm}

Step 13

5.4.7 Circular pitch

96%

114 rated

Answer

Circular pitch can be calculated using:

\text{Circular pitch} = 3 \times m \times \pi = 3 \times 3 \times \pi \approx 9.43 ext{ mm}

5.1 A spur gear with 118 teeth must be cut on a universal milling machine - NSC Mechanical Technology Automotive - Question 5 - 2017 - Paper 1

Worked Solution & Example Answer:5.1 A spur gear with 118 teeth must be cut on a universal milling machine - NSC Mechanical Technology Automotive - Question 5 - 2017 - Paper 1

5.1 A spur gear with 118 teeth must be cut on a universal milling machine. Calculate the indexing required to cut this gear with the help of a Cincinnati dividing head.

5.2 Use simple line sketches to explain the difference between up-cut milling and down-cut milling on a milling machine. Indicate the work-piece feed and cutter rotation.

Up-cut Milling

Down-cut Milling

5.3.1 The width of the key:

5.3.2 The thickness of the key:

5.3.3 The length of the key:

5.3.4 The thickness of the key at the smaller end:

5.4.1 Addendum

5.4.2 Dedendum

5.4.3 Clearance

5.4.4 Pitch circle diameter

5.4.5 Outside diameter

5.4.6 Cutting depth

5.4.7 Circular pitch

Join the NSC students using SimpleStudy...