If you have been following along with the previous shoulder width alteration posts then you may be wondering about what happens to the sleeve cap after this alteration. Let's start by getting one thing out of the way:
Don't overthink the sleeve cap height. The sleeve cap should have been drafted with the assumption that the shoulder seam hits in the right place. Sleeve cap height rarely correlates to shoulder width (it has its own limitations to be addressed at a later blog post). It does not need to move up or down proportionately to how much you moved the shoulder seam for a better fit.
Check to see if the same sleeve cap fits into the revised armhole. Sometimes the sleeve cap won't fit into the same armhole. To fix this we need to be very diplomatic with adjustments.
First, let's see what kind of numbers we are working with:
- Mark your seam allowance and measure along the front armhole curve, on the marked sewing line.
- Repeat the same for the back armhole. **Tip- write your number on the pattern pieces so you can keep track.
- Now, mark the sleeve seam allowance and measure along the sew line on the front cap to the shoulder notch. Write down this measurement. Repeat for the back cap to the shoulder notch.
What the numbers mean: ideally, we are looking for the same measurement on the sleeve cap and armhole. This means no ease. Yes, I said it, no ease. It's fussy to work with and very rarely serves an actual function (but there are many implications that merit a later post). For demonstration purposes, our goal is to get the same measurement.
Less is more: I don't really like making sleeve cap changes more than 1/4" (.6cm), each side of cap, at a time as the shape tends to distort in problematic ways. With that in mind I can extend the sleeve at both sides at the underarm. If that does not yield the number that I need than I can build up the sleeve cap a touch. I try not to mess with the sleeve cap height too much, so I only go in 1/8" (.3cm) increments and recheck my measurements.
If it is still far off then I may adjust the armhole, but dropping or raising only at the underarm. Once again, in no more than 1/4" (.6cm) increments at a time.
Of course, there are always exceptions. If you just can't get the sleeve cap to fit by doing this, than you may have to accept having some ease in your cap.
Hope this is clear and helps you to understand the best practice for aligning the sleeve to the armhole.