Name three (3) types of projections used on drawing.

Here are the answers to question 21 and two other questions from the section.

20. Name three (3) types of projections used on drawing.

• Orthographic Projection
• Isometric Projection
• Oblique Projection

21. A cast iron bearing block is shown in fig 1. Draw the following views using 1st angle projection (i) Front Elevation (ii) End Elevation (iii) Plan.

As an AI, I cannot physically draw the views, but I can describe how to construct them based on the provided isometric drawing and 1st angle projection principles.

• Interpretation of Hole Dimensions: The two $\phi$5mm holes are located on the top surface of the lower block. The dimension "30mm" indicates the distance from the right edge to the center of the holes along the width. The dimension "40mm" indicates the distance from the front edge to the center of the front hole. The "40mm" between the holes indicates the distance between their centers along the depth. However, this would place the second hole outside the block's depth. A more common interpretation for such a layout is that the "40mm" between the holes is the distance between them, and the "40mm" from the front edge refers to the centerline of the two holes.

  • Assuming the 40mm from the front edge is to the centerline of the two holes, and the 40mm between the holes is their spacing:
    • X-coordinate of hole centers (from left edge): $65 \text{ mm} - 30 \text{ mm} = 35 \text{ mm}$.
    • Y-coordinate of front hole center (from front edge): $40 \text{ mm} - (40 \text{ mm} / 2) = 20 \text{ mm}$.
    • Y-coordinate of back hole center (from front edge): $40 \text{ mm} + (40 \text{ mm} / 2) = 60 \text{ mm}$.
  • Both holes are $\phi$5mm.

• (i) Front Elevation (View from "FRONT" arrow):

  • Draw a rectangle representing the overall width (65 mm) and total height (40 mm for the base + 5 mm for the step = 45 mm).
  • The L-shaped part on the left will be visible: a vertical section 20 mm wide and 40 mm high, and a horizontal section on top of it, 20 mm wide and 40 mm high from the base.
  • The step on the right will be visible: 30 mm wide and 5 mm high, starting from the 40 mm height mark.
  • The two $\phi$5mm holes will appear as hidden lines. They are located at 35 mm from the left edge. Draw two dashed lines (representing the diameter) from the top surface of the lower block (at 40 mm height) down to the bottom, centered at 35 mm from the left edge.

• (ii) End Elevation (View from "END" arrow - Right Side View):

  • Draw a rectangle representing the overall depth (70 mm) and total height (45 mm).
  • The main base block will be visible: 70 mm deep and 40 mm high.
  • The step on the right side of the front view will be visible on the right side of this view: 70 mm deep and 5 mm high, sitting on the 40 mm high base.
  • The vertical part of the L-shape (20 mm wide in front view) will appear as a hidden line at 20 mm from the front edge (left side of this view), extending 40 mm high.
  • The horizontal part on top of the L-shape (30 mm deep in the isometric view) will be visible as a rectangle 30 mm deep and 40 mm high, starting from the front edge (left side of this view).
  • The two $\phi$5mm holes will appear as hidden circles in this view. Their centers are at 20 mm and 60 mm from the front edge (left side of this view), and their vertical position is centered within the 40 mm height of the lower block.

• (iii) Plan (View from "PLAN" arrow - Top View):

  • Draw a rectangle representing the overall width (65 mm) and overall depth (70 mm).
  • The L-shaped part will be visible: a 20 mm wide section extending 70 mm deep from the left edge, and a 20 mm wide by 30 mm deep section on top of it, starting from the front left corner.
  • The step on the right will be visible: 30 mm wide and 70 mm deep, starting from the right edge.
  • The two $\phi$5mm holes will appear as visible circles.
    • Center of front hole: 35 mm from the left edge, 20 mm from the front edge.
    • Center of back hole: 35 mm from the left edge, 60 mm from the front edge.

22. Construct an ellipse using the two circle method major axis 60 mm and minor axis 30 mm.