Great video George.
I teach scale drawing as part of my Geometry class. It's one of the topics I like best because it is practical. No one asks "why do I need this?" The video made it clear that there are reasons for using different scales - the larger the scale, the more detail it allows you to show. But using too large a scale would also make it difficult to fit everything on the page.
The key concept in math is the notions of proportion and similarity. While some figures, like triangles, can be similar (same shape) just based on the angles, others require special care. The sides must alll be in the same proportion - must use the same scale. Otherwise, you could end up building something that looks nothing like the drawing - or more likely, will have parts that don't fit together.
Nice post. hanks for the useful info. I can steal this for my class. :)
Greg