My favorite t-shirt company went out of business and I really loved the fit of their t-shirts. The best solution I could come up with was to recreate the pattern by doing a rub-off of one of the t-shirts. This pattern is for my own personal use, but you will find many pattern makers who do rub-offs of existing styles as a starting point. This is one way to study how another pattern maker developed their pattern. I have done this in the industry too, but the resulting style was not an exact copy and bore no resemblance to the initial style. Copying a style in this way for the sake of reproducing an identical product to sell is another thing entirely.
You can see the resulting shape of the pattern that I rubbed-off or traced. The armhole is symmetrical for the front and back bodices, which is fairly typical for t-shirts. Technically, the armhole should be different front to back and if you have fit issues, this would be one place to adjust. For now, I'm leaving it alone.
The original pattern also had binding on the neck and sleeves. I wasn't sure how to accomplish that and have it look neat on a home sewing machine. I think there may be a way that I'll play with later. At this point, I added seam allowances for a narrow neck ribbing.
Patterns for knits are designed with the amount of stretch AND recovery. The original t-shirt had some spandex, which means it stretches and recovers a bit better than a 100% cotton jersey. The original t-shirt is pretty slim fitting because of the spandex and because it is meant as a layering t-shirt to wear under other tops. I wanted to have a pattern I could use with 100% cotton jerseys, so I plan on adding a bit of extra wearing ease.
I noted the amount of stretch for the original knit fabric on the pattern. The stretch ruler is found in the Armstrong pattern drafting book. I'll target my knit fabric shopping for between 50-60% stretch - just have to remember to take a copy of the stretch ruler. I do have some stash knits but it has taken me over a week to find it. More on that later...