Set-In Sleeves: How do they work?

I'm always amazed when I set in a sleeve cap and it works out. I never think it will, but it usually does. I guess my mind doesn't bend in the same sort of curves that a set-in sleeve does!

The Refined Aran Cardigan by Pam Allen. Download your free pattern now!

How does it work? Pam Allen, the designer of one of my favorite (and free!) cardigan knitting patterns—the Refined Aran Cardigan—is here to tell us how.

Sleeve Caps: A Love Affair

There was a time when I was baffled by the construction of sleeve caps. Although I would leap into a sweater design with gusto, knitting the back, front, and sleeves to the armhole lickety-split, I found myself faltering at the prospect of working the cap. It was fudging on a major scale—a matter of gritting my teeth, closing my eyes, and knitting a series of decreasing rows till I had what seemed an appropriate shape. The telling moment, of course, was when I tried to match the upside-down U of my cap into the round armhole opening of my garment. Would it fit? Maybe with a few more rows? A few less?

I've spent a lot of time learning-through more trial and error in the wee hours than I care to remember-how to design a fitted sleeve and its cap. There are standard formulas, true, but I've never been a fan of the one-formula-fits-all approach. The way a sleeve fits and the construction of the cap contributes more to the look and feel of a garment than we generally credit. We all recognize a 1940s jacket or sweater by its long, narrow sleeve cap and squared shoulder. And the high, tight armhole and narrow-shouldered silhouette of a poor-boy sweater date it indelibly from the 1960s. Understanding how the symbiotic trio of armhole, sleeve, and sleeve cap contribute to the look of a garment and, more importantly, how they relate to each other is all-important in sweater design.

Although it's possible to knit up a sleeve by tinkering this way and that, it's far more satisfying to be able to plan a cap that will fit perfectly into its armhole from the get-go. And to do that, you need to understand how sleeves, caps, and armholes relate to each other.


THE TRIO: ARMHOLE, SLEEVE, AND CAP Picture first the curved edge of a garment's armhole, starting from the initial armhole bind off, curving up to the shoulder and down the opposite side (Figure 1A). The measurement of this curve is a fixed entity. Now picture a sleeve cap. Although the shape of the cap doesn't correspond to the cutout of the armhole—these aren't puzzle pieces that fit together as positive and negative shapes—the actual line of the perimeter of the cap needs to measure the same, or slightly more than, the armhole edge to fit in neatly (Figure 1B). The perimeter of the cap consists of the bound-off stitches at the armhole, the bound-off stitches at the top of the cap and the curved and/or tapered sides between them.

Although you can design a cap that has a perimeter measurement equal to that of the armhole, and let the knitted fabric give over the curve of the arm at the shoulder, I like to add a little ease at the top of the cap to build in a little roundness for the arm. If the perimeter of the sleeve cap is too long, however—more than 2 inches—the sleeve cap, eased in, will pucker. If it's too small, the armhole of the garment will pucker, and the sleeve cap will be stretched along the armhole seam.

Now think about the lower part of the sleeve. The width of the sleeve at the upper arm is what determines the shape of the sleeve cap. Each of the caps in Figure 2 has the same perimeter, but each one is shaped differently to maintain the length of the perimeter. If we widen the sleeve, the cap must grow shorter and flatter. If we narrow the sleeve, the cap must be taller and narrower. You can test this yourself with a flexible tape measure.

Measure out 16 inches. If you hold both ends 12 inches apart (a narrow sleeve width) the curve mimicking the cap is tall and narrow. If, however, you spread the ends out to 14 inches, the curve of the tape measure flattens out and the height shrinks. Within those 16 inches of tape, whether the ends are 12 inches or 14 inches apart, you can adjust and play with the curve of the pretend cap. In real life, as long as the perimeter of the cap measures the same as that of the armhole, you can shape your cap in different ways—and each time, it will fit. Read more . . .

—Pam Allen, from Interweave Knits, Winter 2007

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P.S. Do you have any tips for knitting set-in sleeves? Share them with us in the comments!

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