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How do you scale a metric drawing?

Published in Drafting 4 mins read

Scaling a metric drawing involves resizing it proportionally, either larger (scaling up) or smaller (scaling down), while maintaining accurate dimensions based on a specific ratio or scale factor. Here's a breakdown of the process:

Steps to Scale a Metric Drawing

  1. Determine the Current Scale (if any): If the drawing already has a scale noted (e.g., 1:100), understanding this is your starting point. If it's a 1:1 scale, the drawing represents the actual size.

  2. Decide on the New Scale: Determine the desired scale for the resized drawing. Common metric scales include 1:10, 1:20, 1:50, 1:100, 1:200, 1:500, 1:1000, etc. A smaller number in the ratio indicates a larger drawing, and vice versa. For example, 1:50 will result in a larger drawing than 1:100 when representing the same object.

  3. Calculate the Scale Factor: Divide the new scale by the original scale (if any). If there is no existing scale, you can think of the original scale as 1:1. For instance:

    • Scaling up: If you want to change from 1:100 to 1:50, the scale factor is (1/50) / (1/100) = 2. This means the drawing will be twice as large.
    • Scaling down: If you want to change from 1:50 to 1:100, the scale factor is (1/100) / (1/50) = 0.5. This means the drawing will be half the size.
    • Scaling from 1:1: If you want to change a 1:1 drawing to 1:10, the scale factor is (1/10) / (1/1) = 0.1.

  4. Measure Key Dimensions: Carefully measure the critical dimensions of the original drawing in metric units (millimeters, centimeters, or meters).

  5. Apply the Scale Factor: Multiply each measured dimension by the calculated scale factor. This will give you the new dimensions for the scaled drawing.

    • Example: If a wall is 5000 mm long at a scale of 1:100, and you are scaling to 1:50 (scale factor = 2), the new length will be 5000 mm * 2 = 10000 mm.

  6. Redraw the Drawing: Using the new dimensions, redraw the drawing at the desired scale. Ensure all elements maintain their relative proportions.

Methods for Scaling

  • Manual Scaling: Use a ruler, compass, and protractor to redraw the drawing point by point, based on the calculated dimensions.
  • Using a Pantograph: A pantograph is a mechanical linkage used to copy drawings at different scales.
  • Digital Scaling (CAD Software): CAD (Computer-Aided Design) software allows for precise scaling and modification of drawings. Simply input the desired scale factor, and the software will automatically resize the drawing. Programs like AutoCAD, Revit, and SketchUp are commonly used. This is generally the most accurate and efficient method.

Example Scenario

Let's say you have a floor plan at a scale of 1:200, and you need to rescale it to 1:100.

  • Original Scale: 1:200
  • New Scale: 1:100
  • Scale Factor: (1/100) / (1/200) = 2

If a room is 4000 mm wide on the 1:200 drawing, it will be 4000 mm * 2 = 8000 mm wide on the 1:100 drawing. You would then redraw the floor plan using these new, scaled dimensions.

Important Considerations

  • Accuracy: Careful measurement and precise calculations are crucial for accurate scaling.
  • Units: Maintain consistent metric units throughout the process.
  • Complex Shapes: For complex shapes, break them down into simpler geometric elements for easier scaling.
  • Distortion: Be aware that manual scaling can introduce slight distortions. Digital scaling methods generally provide higher accuracy.

By following these steps, you can effectively scale a metric drawing to the desired size while preserving its accuracy and proportions.

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