| Determining sett by getting the diameters on a ruler is easy to do with a heavy yarn, but it would be terribly hard with a slippery, or nubbly, or fine thread. There’s a way to find the diameters using a pencil, paper and an inexpensive calculator. For me, this makes finding the sett a piece of cakeÑno hassle or worry that the threads are touching too much or not enough. This method of calculating the diameters was worked out by Mr. Ashenhurst long ago for industry.This calculation will give you the number of diameters which will determine the maximum sett for a fabric. The reason you want to know the Ashenhurst number (the maximum sett) is that it’s his number that is used to make allowances for yarns, weave, shrinkage, finishing, purpose (e.g. upholstery or sheer curtains, etc.).Using Ashenhurst’s formula, you will find that the number of diameters will be more than if you wrapped the yarn on a ruler. I think the reason his number for diameters is higher is that it’s a mathematical formula which he found to work. The two methods (Ashenhurst and wrapping) can be compared. You can use whichever method seems convenient to you. Surely, you would use Ashenhurst for a warp of sewing thread. It’s likely that you would use the wrapping method for a large wool yarn. But, remember, you will get different numbers if you compare both methods on the same size thread. If you wrapped a yarn and counted the diameters, and you took 1/2 of that number for plain weave, you would need to divide that number by 0.7 to get a number close to Ashenhurst’s.An example might be a yarn wrapped 10 times on a ruler (=10 diameters/inch). Half of that is 5, for plain weave. Divide 5 by .7 to get a number that about equals Ashenhurst’s maximum sett for plain weave.5 divided by .7 = 7
The maximum sett would be 7, not 5. Before I give you Ashenhurst’s formula, you need to understand that you’ll have to push a special key on your inexpensive calculator. It’s the square root key and looks a lot like a check. See Figure.
 Calculator for Ashenhurst To find the square root of a number, enter the number on your calculator then push the square root key. |
Now for the formula:Number of diameters per inch = .9 times the square root of the yards per pound Square root for Ashenhurst sett calculation
That’s it!! That gives you the number of diameters of the yarn in an inch (the calculated number). (On the calculator enter in the yards per pound, then push the square root key. Multiply that number by .9). For example, take a yarn that has 1,000 yds per pound.  Ashenhurst calculation for sett
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| The reason I like this method is that it’s so fast and reliable–no worrying whether the yarns are wrapped properly on the ruler.It’s as simple as pushing a few keys on the calculator. Remember, I said you could compare the two methods–wrapping and Ashenhurst. To make the wrapping method equal to the Ashenhurst, divide the wrapping sett by .7. That will increase the number arrived at by wrapping, so it will give you the Ashenhurst maximum sett. |
Read more in Weaving for Beginners and Book #1: Winding a Warp & Using a Paddle