I’ve been drafting patterns using a copy of Louis Devere’s The Handbook of Practical Cutting on the Centre Point System (1866) for almost two years now. Of the available drafting manuals from the Civil War period, this seems to be the most complete and easiest to learn.
Some Mathematics
One of the more difficult concepts to understand is how Devere varies the size of a pattern. He uses a size 18 3/4 breast as the basis for all of his patterns, which is equivalent to a 37 1/2 chest. This is called the proportionate model. If you are lucky enough to have a 37 1/2 chest (and the other corresponding measurements are the same), you can draft the patterns as they are straight from the book, with a normal ruler . Unfortunately, very few people fit these measurements, so adjustments have to be made.
Let us suppose we have a gentleman with a 42 inch chest, and want to find the correct balance. On a 37 1/2 inch proportionate model, the balance is 2 1/2. But a 42 inch chest would make that larger. First, you need to find the correct ratio between the 42 inch chest, and the proportionate chest. That would look like this:
42 / 37.5 = 1.12After getting the number of 1.12, we multiply that by the balance measurement (or whatever measurement we need to get):
1.12 * 2.5 = 2.8Then, it’s a matter of converting that 2.8 decimal into inches. This comes out to somewhere between 2 3/4 and 2 7/8. As you can see, this method is not very accurate, and prone to mathematical errors. And it takes a long time when you have to do 20 or 30 measurements this way.
Graduated Rulers
Luckily, Devere was a fairly smart man. He devised a set of rulers, called Graduated Rulers. The graduated rulers are, “a series of measures, which are successively graduated larger and smaller than the common inch measure, and are used to draft patterns for larger or smaller sizes than the 18 3/4 breast.” What does this mean? Instead of doing those calculations above, you simply choose a correct sized ruler and then draft the pattern as it is in the book.