Lesson Notes By Weeks and Term v4 - SHS 2
ENGINEERING MATERIALS, TOOLS, AND MACHINES
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ENGINEERING MATERIALS, TOOLS, AND MACHINES
Download the Lessonotes Mobile Ghana app for faster lesson access on Android and iPhone.
Subject: Applied Technology
Class: SHS 2
Term: 1st Term
Week: 9
Grade code: 2.2.1.LI.2
Strand code: 2
Sub-strand code: 1
Content standard code: 2.2.1.CS.1
Indicator code: 2.2.1.LI.2
Theme: METAL TECHNOLOGY
Subtheme: ENGINEERING MATERIALS, TOOLS, AND MACHINES
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In Ghana, from the local mechanic at Kokompe or Suame Magazine to the large-scale construction company building our roads and homes, the ability to create precise holes and shape metal is fundamental. This lesson introduces you to the essential tools and machines that make this possible: the twist drill, the drilling machine, and the grinding machine. Mastering these tools is not just about passing an exam; it's about gaining practical skills that can be used to repair items at home, create new products, or even start a small fabrication business making things like burglar proofs, gates, or farm implements.
This section is divided into three main parts: The Twist Drill, The Drilling Machine, and The Grinding Machine. Part A: The Twist Drill
A twist drill is a rotary cutting tool used to create round holes in various materials. It is the most common type of drill bit used in workshops. Material: Most twist drills are made from High-Speed Steel (HSS). This material is chosen because it is very hard and can withstand the high temperatures generated during drilling without losing its sharp cutting edge. Main Parts of a Twist Drill:
![A simple diagram showing the parts of a twist drill would be drawn on the board here: Shank, Body with Flutes, and the Point.] Shank: This is the end of the drill that is gripped by the chuck of the drilling machine. Straight Shank: Most common for smaller drill sizes. It is perfectly cylindrical. Taper Shank: Used for larger drill sizes. It is a cone shape (Morse taper) that fits directly into the machine's spindle, providing a stronger grip. Body: The main section of the drill, which contains the flutes. It is slightly smaller in diameter at the shank end than at the point end (this is called 'back taper') to prevent the drill from binding in the hole. Flutes: These are the spiral grooves that run along the body of the drill. They serve two critical purposes: They form the cutting edges at the point of the drill. They act as channels to evacuate the cut material (chips or swarf) out of the hole and allow cutting fluid (coolant) to reach the cutting point. Point (The Cutting End): This is the business end of the drill. Cutting Lips: These are the two sharp edges that do the actual cutting. They must be of equal length and at the same angle for the drill to cut a clean, accurate hole. Point Angle: The angle formed at the tip of the cutting lips. The standard angle for drilling mild steel is 118°. For harder materials, a larger angle (e.g., 135°) is used, and for softer materials like plastic or aluminium, a smaller angle (e.g., 90°) is used. Chisel Edge: A small, blunt edge at the very centre of the drill's tip. It does not cut well but pushes material out of the way to start the hole. Lip Clearance Angle: This is the angle ground behind the cutting lip. It ensures that only the sharp cutting edge touches the workpiece, preventing the rest of the drill point from rubbing and causing friction. Part B: The Drilling Machine (Pillar/Bench Type)
A drilling machine is a stationary power tool used to rotate a twist drill and feed it into a workpiece to create a hole. The pillar drill is very common in school workshops. Major Parts and Their Functions: