5.1 State TWO disadvantages of cutting tapers on a centre lathe machine using the compound slide method - NSC Mechanical Technology Fitting and Machining - Question 5 - 2023 - Paper 1

To calculate the length of the taper, we can use the formula:

$$L = \frac{D - d}{2 \tan{\theta/2}}$$

Where:

• D = 78 mm (larger diameter),
• d = 55 mm (smaller diameter),
• \theta = 8° (included angle). So,

1. First, calculate (L):

\tan{4^{\circ}} = \frac{78 - 55}{2L} = \frac{23}{2L}\

Solving for L gives:

$$2L = \frac{23}{0.0699926811} \ L = 164.46 \text{ mm}$$

To find the tailstock set-over, we use the formula:

\text{Set-over} = \frac{L(D - d)}{2}\

Where:

• D = 78 mm,
• d = 55 mm,
• L = 164.46 mm. Calculating gives:

$$\text{Set-over} = \frac{164.46(78 - 55)}{2} = 19.89 mm$$

For a parallel key suitable for an 83 mm diameter shaft, we compute:

Width:

$$\text{Width} = \frac{D}{4} = \frac{83}{4} = 20.75 \text{ mm}$$

Thickness:

$$\text{Thickness} = \frac{D}{6} = \frac{83}{6} = 13.83 \text{ mm}$$

Length: The length is calculated as:

$$\text{Length} = 1.5 \times D = 1.5 \times 83 = 124.50 \text{ mm}$$

A. Side and face cutter / Milling cutters.

B. Arbor / Spacers / Spindle / Axle.