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The wheel shown is to be turned on a lathe from a 30 mm diameter aluminium bar - Leaving Cert Engineering - Question a - 2014
Question a
The wheel shown is to be turned on a lathe from a 30 mm diameter aluminium bar. Describe any three of the turning operations used to produce the wheel. (b) Explain ... show full transcript
Worked Solution & Example Answer:The wheel shown is to be turned on a lathe from a 30 mm diameter aluminium bar - Leaving Cert Engineering - Question a - 2014
Step 1
Describe any three of the turning operations used to produce the wheel.
Answer
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Facing: This operation involves positioning the cutting tool perpendicular to the axis of the lathe and moving it along the spindle. This creates a flat surface on the end of the aluminium bar. This is the first step in preparing the part for subsequent operations.
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Parallel Turning: In this process, the cutting tool is moved parallel to the axis of the lathe. The tool cuts continuously, reducing the diameter of the bar and forming a cylindrical shape. This is essential for achieving the required dimensions of the wheel.
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Taper Turning: In taper turning, the top side of the cutting tool is set at half the included angle of the taper. The cutting tool is then fed at an angle to the axis of the lathe. This results in creating a gradual reduction in diameter, which is significant for wheels that require a specific taper for fitting or aesthetic purposes.
Step 2
Explain any three of the following: Centre drill
Answer
A centre drill is a tool specifically designed for creating a starting point for drilling. It is crucial for ensuring that other drill bits do not wander off-center when being used. The centre drill has a pointed tip that allows it to establish a precise hole in the workpiece, ensuring alignment and accuracy in subsequent operations.
Step 3
Explain any three of the following: Rake angle
Answer
The rake angle is ground on the cutting tool’s edge, which allows for a sharper cutting edge to be effective when machining. A proper rake angle enhances cutting efficiency and reduces friction, allowing the cutting edge to perform better and prolonging tool life. It also helps in controlling the flow of the chips during the cutting process.
Step 4
Explain any three of the following: Knurling
Answer
Knurling is a process used on a lathe to create a patterned surface on the workpiece, which provides a better grip. During this operation, a knurling tool with specific designs is applied to the rotating workpiece. As the workpiece rotates, the knurling tool presses against it, causing a series of grooves or diamonds to form, which enhances its aesthetic appeal and functional grip.
Step 5
Explain any three of the following: Clearance angle.
Answer
The clearance angle on a cutting tool reduces the contact between the workpiece and the cutting tool, which minimizes friction and heat generation during machining. This is essential for preventing tool wear and ensuring a longer tool life. A sufficient clearance angle lets the tool slide over the workpiece without unnecessary resistance, improving cutting efficiency.
Step 6
Step 7
Describe two operations that can be performed on a centre lathe using the part shown.
Answer
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Drilling: The tailstock can be used to hold a drill bit for drilling holes in the workpiece. This involves aligning the drill with the centre and feeding it into the workpiece.
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Supporting Workpieces: The tailstock can support a long bar or shaft, helping to maintain stability as the workpiece rotates during turning operations. This support is crucial for achieving precision cuts.
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Step 10
Describe one advantage of a CNC lathe over a manual lathe.
Answer
One significant advantage of a CNC lathe is its ability to produce complex geometries with high precision and repeatability. Unlike manual lathes, CNC lathes can automate the machining process, reducing the likelihood of human error and increasing production efficiency.
Step 11