Orthographic drawing practice

Questions people ask

What is the difference between an isometric and an orthographic drawing?

An isometric drawing is a picture: it shows three sides of an object at once. An orthographic drawing shows one side at a time, flat, so its sizes can be measured straight off the page.

How do you turn an isometric drawing into orthographic views?

Choose the front. Count the squares you can see from there and draw that outline. Do the same from above and from the side. Add a line wherever a surface steps up or down, and a dashed line for an edge that is hidden behind something.

What is the difference between first angle and third angle projection?

The views themselves are the same. What changes is where they go on the sheet. In third angle the top view sits above the front view and the right-hand side view on its right. In first angle the top view sits below, and the view from the right goes on the left.

What do the first angle and third angle symbols look like?

Both show a cone with its tip cut off, drawn twice: from the side, and from its narrow end as two circles. In the third angle symbol the circles are beside the cone's narrow end. In the first angle symbol they are beside its wide end. The sheet on this page draws the one you choose, in its title block.

Which one should I use?

Third angle is the usual choice in the United States, Canada and Australia, and first angle in most of Europe and in India. Use the one your course or exam board asks for, and show it with the symbol in the title block.