Proportional Dividers

Their Purpose             
                       
One of the purposes of a proportional divider is to transfer a set of measurements from one scale to another. The process of scaling is used to make a drawing or a diagram larger or smaller in terms of absolute size while keeping the same proportions. Another use for the divider is to divide a line or a circle into any number of equal parts.

What The Tool Looks Like

A proportional divider has two legs which are the exact same length and have a point on each end. Connecting the two legs is a pivot point which can be adjusted according to the precise ratio that is required. This ratio can also be made to equal to that between the two scales.

Running down the length of each of the legs is an open slit which is rounded at both ends. Numbers and marks are indicated all along this slit, much as on a ruler, and a small metal slide fits within; it is this piece that you move when you want to adjust the size of the line or circle that you are making. The steel needle points of the legs can be replaced.

Who Uses These Tools?

The proportional divider is a very valuable tool for people with a variety of jobs. Architects in particular have great use for these tools, which can help them to determine the proportions among the various parts of buildings, both inside and out. Architecture is a field in which accuracy of measurement and proportion is of the utmost importance; the slightest mistake can throw everything else off. A PD can be used for many other structural engineering jobs for which precision is similarly required, including the designing of cars, furniture, computers, vacuum cleaners, ovens and other machines.

PDs are, however, useful for much more than putting together objects that serve utilitarian purposes. They can be an important tool for the artist as well, specifically for the sculptor. (Need we remind you that sculpture has long been a part of architecture?) You can use a PD to see how the different parts of the human body relate in size to one another, which is something that often causes difficulty for the beginning artist. It can even help you to learn how to draw!

How to Use a Divider

Basically, if you know how to use a pair of compasses, then you can easily use a divider. The range of proportions on the legs generally runs from 1:1 to 1:10. Holding the tool in one hand, stretch your arm out directly in front of you and place whatever you want to draw or diagram so that you can see it through the opening in the divider. The distance between the legs should reflect the size of the object as seen from that distance. Then position the divider on paper and mark the positions of the legs with a pencil.