FIGURE 5.1 below shows the set-up of a taper with an included angle of 8°, to be machined between centres. 5.1.1 Calculate the small diameter (d) of the taper. 5.1.2 Calculate the tailstock set-over required for cutting the taper in FIGURE 5.1. 5.2 Calculate the following dimensions of a parallel key suitable for a 42 mm diameter shaft: 5.2.1 Width 5.2.2 Thickness 5.3 State TWO advantages of down-cut milling. 5.4 Use a neatly labelled sketch to show straddle milling.

NSC Mechanical Technology Fitting and Machining Basic calculations: FIGURE 5.1 below shows the set-u

FIGURE 5.1 below shows the set-up of a taper with an included angle of 8°, to be machined between centres - NSC Mechanical Technology Fitting and Machining - Question 5 - 2019 - Paper 1

Question 5

FIGURE-5.1-below-shows-the-set-up-of-a-taper-with-an-included-angle-of-8°,-to-be-machined-between-centres-NSC Mechanical Technology Fitting and Machining-Question 5-2019-Paper 1.png

FIGURE 5.1 below shows the set-up of a taper with an included angle of 8°, to be machined between centres. 5.1.1 Calculate the small diameter (d) of the taper. 5.1... show full transcript

Worked Solution & Example Answer:FIGURE 5.1 below shows the set-up of a taper with an included angle of 8°, to be machined between centres - NSC Mechanical Technology Fitting and Machining - Question 5 - 2019 - Paper 1

Step 1

Calculate the small diameter (d) of the taper.

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Answer

To calculate the small diameter of the taper, we first need to determine the length of the taper and apply trigonometric principles.

Using the tangent function:

\tan\left(\frac{\theta}{2}\right) = \frac{AB}{300}

Given that the angle (\theta = 8^\circ),

AB = \tan\left(4^\circ\right) \times 300 \approx 20.98 \text{ mm}

Now, we can find the small diameter (d):

\begin{align*} d &= D - 2AB \ &= 200 - 2(20.98) \ &= 200 - 41.96 \ &= 158.04 ext{ mm} \end{align*}

Step 2

Calculate the tailstock set-over required for cutting the taper in FIGURE 5.1.

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Answer

To find the tailstock set-over, we can establish a direct proportion from the values already calculated.

Using the relation:

\text{Set over} (x) = \frac{300}{400} \times 20.98

Thus, substituting the numbers:

X = \frac{300 \times 20.98}{400} \approx 27.97 \text{ mm}

Step 3

Calculate the following dimensions of a parallel key suitable for a 42 mm diameter shaft: Width.

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Answer

The width of the parallel key can be calculated as:

\text{Width} = \frac{D}{4} = \frac{42}{4} = 10.5 \text{ mm}

Step 4

Calculate the following dimensions of a parallel key suitable for a 42 mm diameter shaft: Thickness.

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Answer

The thickness of the parallel key is given by:

\text{Thickness} = \frac{D}{6} = \frac{42}{6} = 7 \text{ mm}

Step 5

State TWO advantages of down-cut milling.

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Answer

A better finish is obtained.
Friction is reduced.

Step 6

Use a neatly labelled sketch to show straddle milling.

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Answer

A sketch of straddle milling should clearly show:

The work piece.
The milling cutters.
The arbor holding the cutters.

Label each component for clarity.

FIGURE 5.1 below shows the set-up of a taper with an included angle of 8°, to be machined between centres - NSC Mechanical Technology Fitting and Machining - Question 5 - 2019 - Paper 1

Worked Solution & Example Answer:FIGURE 5.1 below shows the set-up of a taper with an included angle of 8°, to be machined between centres - NSC Mechanical Technology Fitting and Machining - Question 5 - 2019 - Paper 1

Calculate the small diameter (d) of the taper.

Calculate the tailstock set-over required for cutting the taper in FIGURE 5.1.

Calculate the following dimensions of a parallel key suitable for a 42 mm diameter shaft: Width.

Calculate the following dimensions of a parallel key suitable for a 42 mm diameter shaft: Thickness.

State TWO advantages of down-cut milling.

Use a neatly labelled sketch to show straddle milling.

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