Here’s a quick and easy way to determine what diameter binding comb you need.
1. Place your document (including covers) on a flat surface.
2. Using a ruler measure the thickness of the document. Do not compress the pages.
3. Add 1/8” to the combined Thickness.
The combined measurement is the correct diameter of comb needed for that document. If the measurement falls between two sizes choose the next larger size comb. One thing to remember is that the holes must be punched to the proper depth when using this formula. Most all plastic binding machines have an adjustment to place the holes the proper depth from the edge of the paper. If you’re not sure how to make that adjustment refer to the owners manual that came with the machine.
This picture illustrates how to make the measurement. The document measures a little more than ¾” so the comb size would be 1”.