Nomograms are visual guides to functional relationships. They can be as simple as a conversion table and complex enough for multi-variate gunnery work(http://myreckonings.com/wordpress/2008/01/09/the-art-of-nomography-i-geometric-design/). In the not too distant past nomograms were able to "provide engineers with fast graphical calculations of complicated formulas to a practical precision."

If you're not shooting cannons (and you shouldn't be), nomograms can be functional and handsome memory aids and computation devices. They can also be made with a limited amount of supplies. I wanted to start making a nomogram with one level of complexity, the ability to add and subtract different numbers, which required a middle value that can vary. A little bit of measuring cutting, guessing, and checking gave me a useful, if not handsome, tool.

Step 1: Tools and Materials

Pencil
Ruler
Utility knife
Tape
Index card
Paper fastener

The tape is optional. I use it to line the guide so the fastener doesn't wear away the paper.

Step 2: Cut Guide

I cut my "4 x 6" card to three inches by five inches. You, however, might just want to use a "3 x 5" card. Then cut a 1/16th inch line in the middle and at least a half an inch from the bottom.This will be your guide line.

Step 3: Guide Numbers

Write numbers next to the guide spaced about a quarter-inch away. You'll want to write them on both sides for maximum visibility.

Step 4:

Write numbers on the far left and right side about 1/2-inch apart. You'll notice that I had to do some adjustment on the placement. You'll also notice that the numbers have an inverse relationship, as the numbers on the left ascend in a descending manner, the numbers on the right descend in a descending manner. Got that?

Step 5: Practical Precision

Insert a paper fastener in the guide. The paper fastener creates an index line. In this example, the index line points from the 26 through the 6 to the 20, displaying the functional relationship: 26-6=20 and 20+6=26.

You'll notice that the pointing is approximate. That's where Mr. Doerfler's phrase "practical precision" comes in handy. You can also use the phrases "close enough for who it's for" and "close enough for government work."

Step 6: Meditations and Explorations

To make a little smooth gliding, I added an index card washer to the back.
As I was making this nomogram, I could see how the far left and right axes had a curvilinear relationship with the center numbers. My next nomogram will emphasize that.
The spindle in the middle would work better if it were transparent and pointed to the edge.
Obviously, you need fairly decent fine motor skills to create nomograms with paper fasteners. How about nomograms for the under eight crowd? You could use a straight edge or a piece of yarn for calculation, or a magnetic board for moving around numbers.
Is there a relationship between curve-stitching devices (http://www.mathcats.com/crafts/stringart.html) and nomograms?
What are the similarities and differences of nomograms, sectors, slide rules, and rulers?