Technical Drawing

Habari Mhandisi! Welcome to the World of Technical Drawing!

Ever looked at the Nairobi Expressway, the magnificent SGR railway, or even the simple, strong design of a Kiondo basket and wondered, "How did they make that?" Before a single piece of steel is cut or a single stone is laid, there's a plan. A very special kind of plan. That plan is a technical drawing, and today, you're going to learn its language!

Forget art class where you draw a beautiful mango tree. In engineering, our drawings need to be so precise that a person in Kisumu can build something exactly the same as a person in Mombasa, just by looking at the drawing. It's the universal language of creators, builders, and innovators. Let's get started!

What is Technical Drawing?

Simply put, Technical Drawing is a way of creating accurate and detailed drawings to communicate information. It’s not about making things look pretty; it's about making things clear. It uses a set of rules, symbols, and conventions so that anyone, anywhere, can understand exactly what needs to be made.

• Artistic Drawing: Focuses on emotion, beauty, and interpretation.
• Technical Drawing: Focuses on facts, dimensions, and clarity.

Image Suggestion: A split-screen image. On the left, a colourful, artistic painting of a sunset over the Maasai Mara. On the right, a crisp, black-and-white technical blueprint of a gear system with precise labels and dimensions. The title above the image says "Art vs. Technical Drawing: Two Languages, Two Purposes".

The Alphabet of Lines: Every Line Has a Meaning

Just like the letters of the alphabet make up words, different types of lines make up a technical drawing. You must learn what each one means. They are our engineering alphabet!

• Continuous Thick Line: This is for the main event! It shows the visible outlines and edges of an object.
• Continuous Thin Line: These are the supporting cast. Used for dimensioning, projection lines, and showing details.
• Dashed Thin Line: The mystery line! It shows hidden features you can't see from the outside, like the inside of a box.
• Chain Thin Line: The centre line. It marks the centre of circles, holes, and symmetrical objects.

Let's see them in action on a simple block:

      +-----------------+
     /                 /|
    /      (A)        / |
   +-----------------+  |  <--- (A) Continuous Thick Line (Visible Edges)
   |                 |  +
   |                 | /
   |      (B)        |/
   +-----------------+

   (B) A hole inside the block would be shown with a
       Dashed Line from the side view.

   (C) A centre line for that hole would be a
       Chain Thin Line (-- . -- . --)

Scaling: Fitting a Gari on a Karatasi!

Imagine trying to draw a plan for a new classroom block on your A4 exercise book. It's impossible to draw it at its actual size! That's where scaling comes in. We draw a smaller (or sometimes larger!) version that is perfectly in proportion.

The scale is written as a ratio. For example, 1:100 (read as "one to one hundred"). This means every 1 unit on your drawing represents 100 units in real life.

• Reduction Scale (e.g., 1:50, 1:100): Making large objects like buildings or cars fit on paper.
• Full Scale (1:1): Drawing an object at its actual size, like a mobile phone.
• Enlargement Scale (e.g., 2:1, 5:1): Making very small objects, like the parts of a watch, bigger so we can see the details.

Let's Do Some Math!

A wall of a house is 6 meters long in real life. You need to draw it on paper using a scale of 1:50. How long will the line on your paper be?

Step 1: Convert everything to the same unit. Millimeters (mm) are standard.
   Actual Length = 6 meters = 6000 mm

Step 2: Understand the scale.
   Scale = 1:50
   This means Drawing Length = Actual Length / 50

Step 3: Calculate the drawing length.
   Drawing Length = 6000 mm / 50
   Drawing Length = 120 mm (or 12 cm)

Answer: You will draw a line 120 mm long on your paper.

Orthographic Projection: Seeing All Sides at Once

This sounds complicated, but the idea is simple. Imagine you have a basic charcoal jiko. Now, imagine it's inside a clear glass box. You look at it from the front and draw what you see on the front glass. Then you look from the top and draw on the top glass. Then from the side, and draw on the side glass.

If you unfold that glass box, you have three different "views" of your jiko on a flat piece of paper. This is Orthographic Projection! It gives us a complete understanding of a 3D object on a 2D surface.

The main views are:

• Front View (or Elevation)
• Top View (or Plan)
• Side View (or End Elevation)

Image Suggestion: A simple, vibrant 3D rendering of a classic Kenyan charcoal jiko. Arrows labeled "Front View", "Top View", and "Side View" point at it. Next to it are the three corresponding 2D orthographic drawings, clearly labeled, showing the jiko's circular top, cylindrical body, and side opening.

Here is a very basic example of an L-shaped block in First Angle Projection (the system we use in Kenya):

      TOP VIEW
   +-----------+
   |           |
   |           |
   +-----+-----+
   |     |
   |     |
   +-----+

      FRONT VIEW        SIDE VIEW
   +-----------+      +-----+
   |           |      |     |
   |           |      |     |
   +-----+-----+      +-----+-----+
   |     |     |      |           |
   |     |     |      |           |
   +-----+-----+      +-----------+

Dimensioning: The Numbers that Matter

A drawing without dimensions is just a picture. It’s useless for building anything! Dimensioning is the process of adding size and location information to your drawing.

A Short Story: The Tale of Two Fundis

Juma, a carpenter, was given a beautiful sketch of a bookshelf. He built it using his eyes, and it looked okay, but the shelves were too short for the big textbooks, and it was too wide to fit in the corner!
His friend, Charles, was given a technical drawing of the same bookshelf. It had dimensions: 800 mm wide, 1200 mm high, shelves 300 mm deep. Charles built it perfectly. It fit the corner exactly, and every book had its place. Dimensions are the difference between guessing and knowing!

Key Rules for Dimensioning:

• Keep dimensions outside the object outline.
• Use thin, continuous lines (dimension and extension lines).
• All measurements are in millimeters (mm) unless stated otherwise.
• Don't repeat dimensions. Be clear and concise.

Your Turn, Future Engineer!

You have learned the basic language of engineering. You now know that lines talk, scaling makes the impossible possible, and projections let you see around corners!

Your Mission:

1. Find a simple object in your home - a book, a remote control, a small box, or even a bar of soap.
2. Take a piece of paper, a pencil, and a ruler.
3. Try to draw its Front View, Top View, and Side View.
4. Carefully measure the object and add at least three important dimensions (like length, width, and height) to your drawing.

Don't worry about perfection. The goal is to practice thinking like an engineer and communicating your ideas clearly. Keep practicing, and soon you'll be designing the next great Kenyan innovation!