Printer-friendly version

11 July 2003

Mechanical Drawing the Old Fashioned Way, Part 2

by Brian Mansfield

Using Your Tools

Now that we have the tools to create mechanical drawings properly, we need to know how to use them. I would like to talk about the t-square first. The t-square is used to create horizontal lines on your paper. The t-square is also used to align your paper onto the drawing surface (secured by scotch tape at the corners). If your paper does not yet have a horizontal line on it, align the bottom of the paper to the t-square. If your piece of paper already has horizontal lines on it, align the horizontal line to the t-square.

Figure1: Drawing horizontal lines with the t-square.

The triangles along with the t-square can be used to create vertical lines. By themselves, they also can be used to create lines at 45^°, 30^° and 60^°.

Figure 2: Drawing vertical lines with the t-square and triangle.

Together, however, they can be used to create lines at any 15^° increment.

Figure 3: Drawing lines at any 15^° increment with the triangles.

The triangles can also be used to create lines parallel or perpendicular to any line of arbitrary angle. To create parallel lines, align one of the triangles to the line and the other triangle to the first triangle. Move the first triangle along the second and draw the parallel line at the required distance. Drawing perpendicular lines is similar but be careful how you align your first triangle (make sure the 90^o angle is along the line).

Figure 4: Drawing parallel lines to a line of arbitrary angle.

Figure 5: Drawing perpendicular lines to a line of arbitrary angle.

The compass is used to create circles and arcs. If you have circle templates, you may want to use them first. The proper use of a compass is seen in the figure.

Figure 6: Proper form with a compass.

The compass can also be used to transfer dimensions from one portion of your drawing to another. By placing the ends of the compass along a length, this length can now be transferred anywhere else on your drawing.

Keep in mind the rules you learned in geometry about arcs and tangents to them. Such as seen in the following figures.

Figure 7: A tangent line to an arc is perpendicular to a line
drawn from a circles center to the tangent point.

Figure 8: A line drawn between the centers of two tangent
arcs will also pass through the tangent point.

The scale and protractor are used to make precise measurements. The scale has many different sides with many different marks on it. The side that says "16" is full scale. The other sides have other numbers on them for different scales. For instance, the side that says _ means 1" on the scale is actually _" in "real life". To be honest, I never found theses different scales useful. I always liked doing the conversion in my head, but I can see the usefulness of the scale. Use your measuring tools sparingly. Most of the time it is better to transfer or infer a dimension on your drawing using your instruments.

Homework

Practice using your tools by creating horizontal, vertical and arbitrary angled lines. Also, create arcs and tangent lines and arcs.

Next Up

Lettering.