Class: Senior Secondary School 2 (SS2 / SSS2)
Term: Third Term
Week: 9
Age: 16 years
Duration: 45 minutes
Subject: Metal Work
Curriculum Theme: Pre-Vocational Studies
Previous Lesson: Lathe Cutting Tools.
Topic: Shaping and Milling Machines
Subject Matter: Meaning of shaping machine (machine for flat surfaces), parts of shaping machine, milling machine operations (slab milling, climb milling, end milling), direction of rotation of milling cutter, work holding, tool holding

Specific Objectives

By the end of the lesson, pupils should be able to:

Cognitive Domain:

Define a shaping machine.
Identify the main parts of a shaping machine.
Describe different types of milling machine operations.
Explain the direction of rotation of milling cutters.

Affective Domain:

Appreciate the importance of safety when operating shaping and milling machines.
Value the precision achieved by machine tools.

Psychomotor Domain:

Sketch the basic layout of a shaping machine.
Identify various work holding and tool holding devices used on milling machines.

Collaborate effectively during group discussions on machine operations.
Communicate clearly about the functions of different machine parts.

Reference Materials

The following resources were used in planning this lesson:

Senior Secondary Schools Education Curriculum
State Unified Scheme of Work
Metalwork for Senior Secondary Schools Textbook

Instructional Materials

The teacher will teach this lesson with the aid of:

Charts showing diagrams of shaping and milling machines
Pictures of various cutters and work holding devices
A model or real shaping machine (if available)
A model or real milling machine (if available)
Various milling cutters

Rationale for the Lesson

This lesson enables pupils to understand the fundamental principles and operations of shaping and milling machines. This knowledge is important for pupils interested in vocational studies and provides a foundation for careers in manufacturing and engineering.

Prerequisite/Previous Knowledge

Pupils are expected to have basic knowledge of workshop safety, hand tools, and other metalworking processes.

Lesson Content/Board Summary

Shaping and Milling Machines

Meaning of Shaping Machine

A shaping machine is a machine tool used to produce flat surfaces. It operates by moving a single-point cutting tool in a straight line across the workpiece, typically used for creating horizontal, vertical, or angular flat surfaces.

Parts of Shaping Machine

The main parts of a shaping machine include:

Base: Provides the foundation and support for the entire machine.
Column: Houses the driving mechanism and supports the ram.
Ram: Carries the tool head and reciprocates (moves back and forth) to provide the cutting stroke.
Clapper Box: Attached to the tool head, it allows the tool to lift during the return stroke, preventing dragging.
Tool Head: Holds the cutting tool and allows for adjustment of depth of cut and angular settings.
Table: Holds the workpiece and can be adjusted vertically and horizontally.
Cross Rail: Supports the table and allows for horizontal movement.

Milling Machine Operations

Milling is a machining process that uses rotary cutters to remove material from a workpiece by advancing the cutter into the workpiece. Different operations are performed based on the type of cutter and its movement.

Slab Milling (Peripheral Milling)

In slab milling, the cutting action occurs primarily on the periphery (outer edge) of the cutter. The axis of the cutter is parallel to the surface being machined. This operation is used for machining large, flat surfaces.

Climb Milling (Down Milling)

In climb milling, the cutter rotates in the same direction as the workpiece feed. The chip thickness starts at maximum and decreases to zero. This method offers a smoother cut, longer tool life, and reduces the tendency for the cutter to “climb” over the workpiece.

Conventional Milling (Up Milling)

In conventional milling, the cutter rotates in the opposite direction to the workpiece feed. The chip thickness starts at zero and increases to maximum. This method can cause more tool wear and chatter, but it is suitable for workpieces with rough or hard surfaces.

End Milling

End milling uses cutters that have cutting teeth on both the periphery and the end face. It is used for producing slots, pockets, contours, and for facing operations where the cutter’s axis is perpendicular to the surface being machined.

Direction of Rotation of Milling Cutter

The direction of rotation of the milling cutter relative to the workpiece feed determines whether the operation is climb milling or conventional milling. For climb milling, the cutter rotates in the same direction as the feed. For conventional milling, the cutter rotates opposite to the feed.

Work Holding Devices for Milling Machine

Work holding devices secure the workpiece firmly on the milling machine table. Common devices include:

Machine Vices: Used for holding small to medium-sized workpieces.
Clamps and T-bolts: Used for securing larger or irregularly shaped workpieces directly to the T-slots on the machine table.
Rotary Tables: Used for machining circular features, arcs, or for indexing operations.
Indexing Heads (Dividing Heads): Used for accurately dividing a workpiece periphery into equal divisions for gear cutting or polygon milling.

Tool Holding Devices for Milling Machine

Tool holding devices securely hold the milling cutters in the machine spindle. Common devices include:

Arbors: Used for holding shell end mills, side and face cutters, and slab mills. They fit into the machine spindle and support the cutter.
Collets: Used for holding end mills, drills, and reamers with straight shanks. They provide precise concentricity and strong gripping force.
End Mill Holders: Similar to collets but designed specifically for holding end mills securely.

Teaching Methods/Instructional Techniques

Discussion, Lecture, Demonstration, Question and Answer, Visual Aids

Instructional Procedures

Step 1: Introduction

Time: 5 minutes
Teaching Skill: Set Induction
Teacher’s Activity: The teacher greets the pupils and asks them to recall any machine tools they know that are used for shaping metal.
Pupils’ Activity: Pupils respond by mentioning various machine tools like lathes, drilling machines, etc.
Learning Point: Pupils activate prior knowledge related to machine tools.

Step 2: Explanation of Shaping Machine

Time: 5 minutes
Teaching Skill: Explanation
Teacher’s Activity: The teacher explains the meaning and purpose of a shaping machine, emphasizing its use for producing flat surfaces.
Pupils’ Activity: Pupils listen attentively and take notes on the definition of a shaping machine.
Learning Point: Pupils understand what a shaping machine is and its primary function.

Step 3: Parts of Shaping Machine

Time: 5 minutes
Teaching Skill: Identification/Demonstration
Teacher’s Activity: The teacher displays diagrams or models of a shaping machine and points out its major parts, explaining the function of each.
Pupils’ Activity: Pupils observe the diagrams/models, identify the parts, and ask questions for clarification.
Learning Point: Pupils can identify and state the function of key parts of a shaping machine.

Step 4: Introduction to Milling Machine Operations

Time: 5 minutes
Teaching Skill: Explanation
Teacher’s Activity: The teacher introduces the milling machine as another important machine tool and explains its general principle of operation using rotary cutters.
Pupils’ Activity: Pupils pay attention and note the general concept of milling.
Learning Point: Pupils grasp the basic idea of how a milling machine works.

Step 5: Specific Milling Operations

Time: 10 minutes
Teaching Skill: Detailed Explanation
Teacher’s Activity: The teacher explains in detail various milling operations such as slab milling, climb milling, conventional milling, and end milling, using illustrations where necessary.
Pupils’ Activity: Pupils listen, observe, and ask questions to understand the differences and applications of each operation.
Learning Point: Pupils can differentiate between various milling operations and their characteristics.

Step 6: Work Holding and Tool Holding

Time: 5 minutes
Teaching Skill: Elucidation
Teacher’s Activity: The teacher explains the importance of securely holding both the workpiece and the cutting tool, describing common work holding and tool holding devices for milling machines.
Pupils’ Activity: Pupils listen and note down the types of holding devices and their uses.
Learning Point: Pupils understand the methods for securing workpieces and tools on a milling machine.

Step 7: Evaluation/Review

Time: 5 minutes
Teaching Skill: Questioning/Assessment
Teacher’s Activity: The teacher evaluates the learning by asking the following questions:

What is the primary function of a shaping machine?
Mention three main parts of a shaping machine.
Differentiate between climb milling and conventional milling.
List two types of milling operations.
Name two devices used for holding workpieces on a milling machine.

Pupils’ Activity: Pupils answer orally and in writing.
Learning Point: Pupils demonstrate understanding of the lesson.

Step 8: Conclusion

Time: 5 minutes
Teaching Skill: Summarization
Teacher’s Activity: The teacher summarizes the key points of the lesson, reiterating the importance of shaping and milling machines in metalworking. The teacher then gives homework, asking pupils to sketch a shaping machine and label its parts.
Pupils’ Activity: Pupils listen to the summary, ask any remaining questions, and copy the homework.
Learning Point: Pupils consolidate their understanding and are given a task to reinforce learning.

Lesson Keywords

Shaping machine – A machine tool used to produce flat surfaces by reciprocating a single-point cutting tool.
Milling machine – A machine tool that uses rotary cutters to remove material from a workpiece.
Slab milling – A milling operation where cutting occurs on the periphery of the cutter, used for large flat surfaces.
Climb milling – A milling operation where the cutter rotates in the same direction as the workpiece feed.
End milling – A milling operation that uses cutters with teeth on both the periphery and end face, used for slots, pockets, and contours.
Work holding – Devices used to secure the workpiece on a machine tool.
Tool holding – Devices used to secure the cutting tool in a machine tool.

Differentiation

For pupils who grasp concepts quickly, the teacher can challenge them to research different types of cutting tools used for specific milling operations. For those needing more support, the teacher will provide additional visual aids and simplified explanations, focusing on identifying the main parts and basic operations.

Note for teachers using this lesson plan

If actual shaping and milling machines are available, a brief practical demonstration of their parts and movements will greatly enhance pupil understanding. Emphasize safety precautions during any discussion or demonstration of machine tools. Encourage pupils to draw diagrams in their notes to aid memory.