Someone on Ravelry asked what the best way to seam a sweater was. She'd done a nice job knitting, but wasn't happy with her seams. I suggested (as did others) that mattress stitch seams are the best looking. Most online sources, however, show only vertical seams. Some show horizontal seams, but I couldn't find a nice online tutorial that showed how to seam a horizontal edge to a vertical edge, as with a drop-shoulder sleeve.
So here you are. A tutorial for seaming sweater shoulders.
Before you seam, block your pieces. It'll be much easier to seam them if you have flat edges. Since I wanted to get this done an upload it before I got distracted, I did not block my fake sweater pieces. Sue me.
Sewing shoulder seams
I happen to like a nice 3-needle bind off for shoulder seams, but if that's not possible, I seam them like so:
line up the pieces right side up so the bound edges are facing each other. If you are seaming a cardigan, make sure you're sewing the front piece to its correct corresponding back shoulder.
Insert the tapestry needle between the first two stitches
Pull it through, leaving a three or four inch tail.
Next, insert the tapestry needle between the first and second stitches on the opposite shoulder piece. Note that when you look at a stitch upside down, what looks like the middle of a stitch is actually the space between two stitches.
Continue moving from bottom to top, capturing one stitch at a time. Leave plenty of slack.
When you've worked all the way across, pull firmly with both ends of the seaming yarn.
Here's what the seam looks like from the inside:
Seaming the sleeve to the body
First, you need to do a teensy bit of math.
Measure your stitch gauge
Mine is 5 sts/inch
Measure your row gauge.
Mine is 6.5 rows/inch
This tells you how what the ratio of stitches to rows is when you are seaming. In this sample, I have to seam 5 stiches for every 6.5 rows. Because you have to seam whole stitches to whole rows, I can look at it this way: for every 10 stitches, I need to eat up 13 rows. I can alternate 5 sts and 6 rows for one inch with 5 sts and 7 rows for the next.
In my example below, the "sleeve" is 20 stitches wide, which is 4 inches. I marked the point between stitches 10 and 11, and pinned it to the shoulder seam. Then I counted 13 rows down on each side and clipped the 13th row of one body piece to the first stitch on one side of the sleeve, and the 13th rows down of the other body piece to the last stitch on the other side of the sleeve. Like so:
Starting with the sweater body, I slipped the threaded tapestry needle under the horizontal bar between the edge stitch and the next stitch in. The horizontal bar is the running thread that connects one stitch to the other.
Next, I insert the tapestry needle between the first and second stitches under the bound off edge of the sleeve (just like for the bottom shoulder piece. I work back and forth between the body and the sleeve, picking up one horizontal bar on the body for every stitch on the sleeve for several stitches. Remember, based on my row gauge, I need to pick up an extra horizontal bar in the first inch, and two extras in the second inch, so that I pick up 13 rows/horizontal bars for every 10 stitches. Here's how I pick up an extra horizontal bar:
Here I am at the midpoint:
I can tighten it up now, if I want, by pulling on both ends of the seaming yarn:
Here's what the inside seam looks like:
Then I can work the other half the same way: 5 sts and 6 rows, and then 5 sts for 7 rows. Note that when I pick up 5 sts for 7 rows, I work 2 sts with 3 rows, then I work 3 sts with 4 rows. I don't pick up more than 2 horizontal bars/rows at a time.
Here's the end product: