Last year in October, I was well versed in how to do a full bust adjustment in many different types of bodice styles, but now I need to know how to do a small bust adjustment (SBA). I searched for tutorials and in my books, and the directions for a shoulder princess seam are scarce. (I found a brief description at Tilly and the Buttons.) There isn’t even an example in Fitting For Real People! I was shocked about that. So, here’s a tutorial. Basically, you cut the same lines as creating a full bust adjustment, but you overlap pattern pieces instead of spreading. Note – you may not need a shoulder princess seam for fitting, but I think it creates a very nice line and use it on all kinds of garments, including knit shirts.
The first step is to mark lines on the side front panel pattern piece. The lines should point toward the apex. In my case, I guess at where that would have been. The line from the armhole should be approximately 1/3 from the side seam to the shoulder. The line from the side seam should be approximately where a bust dart would be.
The second step is to cut along the lines. Cut from the bottom of the vertical line up to the apex point and then over to the arm scythe, leaving a hinge at the arm scythe seam allowance. That hinge is just an 1/8″, but it’s very important. The other cut is from the side seam to the apex, leaving a hinge at the apex of 1/8″. (These are the directions that are the opposite of a FBA, but I think that the cut from the side seam to the apex is unnecessary. We will not be changing this area.)
Now you can see that the hinges allow you to overlap the pattern pieces. Overlap the pieces so that the cut line from the arm scythe cut moves up and overlaps the main pattern piece. Avoid overlapping at the bust dart area (because this would affect the side seam).
You can also see that as the pattern cuts are overlapped, there is width and length reduced in the pattern. Removing the length from the left side of the side and the front pattern piece is no problem. You can cut that off since you don’t need it to go over the bust.
However, you may need to add width back to the pattern piece. You can do that by cutting up the side seam allowance (leaving a hinge at the point where the side seam and arm scythe meet) and moving it out to the side. Add tissue and tape the seam allowance back. Cutting away the seam allowance and taping it back after adding tissue ensures that your front and back pattern pieces will still fit together.
If you have an extra where the side panel has overlapped the seam where it joins the center front, just true that up to the original seam line.
Finally, I would be remiss if I forgot to mention that you now need to adjust your grain line! That will likely be parallel to the seam line that attaches to the center front panel.
Disclaimer – I’m not a patterncutter. I have done this adjustment and it works. It makes logical sense. but I’m not a professional. Please leave a comment if you see that I’ve made an error here. The sewing community is a place where we learn from each other! : )