You will see that this range described described above holds true.
What an arbitrary criteria for generating the thread size for a given hole! Feel free to check this out on your own, try the 6, 8, and 11 mm hole sizes and see what threads that the Cosmetic Thread feature makes available. For example, the 5 mm hole has a range between 5 and 7.5 mm if you compare this range to the last column on the right-hand side table you will see the corresponding standard threads are M6, M8, M8 x1. All standard sizes within the range become the available thread sizes. This is a range that SOLIDWORKS creates and then compares to the Hole Wizard database on the right, below. On the left, below, you will see a table with 2 columns, first column is the hole size and second column is 1.5* hole size. The Cosmetic Thread feature uses a simple mathematical expression to determine which thread sizes can be assigned to certain hole sizes. I then compared the findings with the Hole Wizard database, see the screenshot below, and made an interesting and rather dull discovery.
I created a simple block then made several holes with increasing diameter dimensions (tangent: this can be easily accomplished by creating a single circular cut and then linear pattern with the vary pattern option) and then checked to see which thread sizes were available with the Cosmetic Thread.
I have tested this for the ISO standard and have discovered a pattern that will demystify this behavior. The first thing that one will discover when using the Cosmetic Thread feature (found on the Insert menu -> annotations flyout) is that not all thread sizes are available when selecting any standard other than “none”. I have encountered some complications and confusion whilst working technical support that I will endeavor to clear up in this blog article. Also, there are a few applications where this is necessary, think about an imported body with holes that need thread callouts as an example. Some customers prefer to cut a circular hole and then add the Cosmetic Thread. Depending on the hole type (counterbore, counter sink, clearance hole, tapped hole, etc) the correct values are referenced and used to create the hole feature. To access this data the only thing that is necessary is to select the standard (ISO, ANSI, etc) and the bolt or screw size. All the geometric data that is required to create the desired hole is in a database that the Hole Wizard references. As a best practice, I always recommend using the Hole Wizard to create cosmetic threads it creates the correct hole size and adds the thread size automatically. Cosmetic threads can be a useful annotation to help manufacture parts.