To set in a sleeve without puckers, sew two rows of long stitches across the sleeve cap between the notches, match the notches (single to the front, double to the back, top of the cap to the shoulder seam) and the underarm seams, then pull the bobbin threads gently until the cap fits the armhole, spreading the fullness over the top of the cap. Steam it to shrink the fullness, pin closely, and sew slowly at the seam allowance.
Why is the sleeve cap bigger than the armhole?
The curved top of the sleeve, the sleeve cap, is drafted slightly longer than the armhole it goes into. That extra length, the cap ease, gives the sleeve room over the round of the shoulder and the top of the arm. On wovens it is typically 1 to 3 cm (3/8 to 1 1/4 in).
Sewly drafts each sleeve cap to its own armhole: the cap equals the armhole length plus 2.5 cm (1 in) of ease on a fitted sleeve, 1.8 cm (3/4 in) on a regular one, 1.2 cm (1/2 in) on a relaxed one and 0.6 cm (1/4 in) on an oversized one. Knit sleeves get no cap ease at all, because the fabric stretches to fit.
Easing means fitting the longer edge to the shorter one without folds. The extra is spread so finely that it disappears into a smooth, rounded cap.
Left sleeve, right sleeve: read the notches
Sleeves are cut as a pair, and the back of each sleeve is marked with a double notch, the front with a single notch. On Sewly patterns the single notch is 7.5 cm (3 in) and the double notch 8.5 cm (3 3/8 in) up from the underarm, and a notch at the top of the cap marks where it meets the shoulder seam. The armholes have matching notches: single on the front bodice, double on the back. Match double to double and a sleeve cannot go in backwards.
Two methods: in the round or flat
| Method | When to use it | Order of work |
|---|---|---|
| In the round | Woven sleeves with cap ease, puff sleeves | Sew the side seams and the sleeve seams first, then insert the sleeve tube into the armhole |
| Flat | Knits, drop shoulders, relaxed sleeves with little ease | Sew the sleeve into the open armhole, then sew the side seam and underarm seam in one line |
The flat method is quicker and is the one Sewly's T-shirt and sweatshirt guides use. The in-the-round method gives more control over cap ease and is used for its woven tops and dresses.
How to set in a sleeve in the round
- Prepare the bodice. Sew the shoulder and side seams, finish them, and press them open.
- Prepare the sleeve. Sew the underarm seam, finish it and press it open. Check the notches are marked.
- Ease-stitch the cap. Set a long straight stitch, 4 to 5 mm (5 to 6 stitches per inch), and loosen the needle tension slightly. With a 1.5 cm (5/8 in) allowance, sew one row 1 cm (3/8 in) and a second 2 cm (3/4 in) from the edge, from the front notch over the cap to the back notch, leaving 10 cm (4 in) thread tails. Do not backstitch. The seam will run between the two rows, which keeps tiny pleats from forming.
- Insert the sleeve. Turn the bodice wrong side out and keep the sleeve right side out. Slip the sleeve into the armhole so the right sides face each other and the raw edges align.
- Match the key points. Pin the underarm seam to the side seam, the top notch to the shoulder seam, the single notch to the front armhole notch and the double notches to the back.
- Draw up the ease. Pull the two bobbin threads from both ends, a little at a time, until the cap fits the armhole. Spread the fullness over the upper cap between the notches, with a little more around the shoulder point. The underarm section below the notches is not eased at all.
- Shrink the fullness. Take the sleeve out, place the cap over a tailor's ham or the narrow end of a sleeve board, and steam the eased area, patting it into a smooth dome. Wool and linen shrink beautifully, cotton reasonably, polyester barely. Use about 150 °C (300 °F) and a press cloth for wool, 200 °C (390 °F) for cotton and linen, 110 °C (230 °F) for synthetics.
- Pin closely. Put the sleeve back and pin every 2 cm (3/4 in) around the cap, pins at right angles to the edge. On slippery or tricky fabric, hand baste instead.
- Sew. With a 2.5 mm stitch (about 10 per inch), start at the underarm and sew at 1.5 cm (5/8 in), between the two ease rows. Many people sew with the sleeve on top so they can see and smooth any tuck as it forms; if the cap has a lot of ease, try it with the sleeve underneath, against the feed dogs, which helps ease it in. Go slowly and stop with the needle down whenever you adjust.
- Check from the right side. Look for any tuck or pleat. If you find one, unpick 5 cm (2 in) around it, redistribute the ease and sew that section again.
- Reinforce the underarm. Sew a second row 6 mm (1/4 in) from the first inside the allowance, from notch to notch under the arm. Trim the underarm allowance to 1 cm (3/8 in) and finish the edges together with a zigzag.
- Remove the visible ease row and press. Pull out the ease row at 2 cm (3/4 in), which sits on the garment side of the seam. Press the seam allowance toward the sleeve, over a ham, pressing only the allowance. Never press the cap itself flat.
How to set in a sleeve flat
- Sew the shoulder seams and press them.
- With the bodice flat and right side up, place the sleeve right sides together on the armhole, top notch to shoulder seam.
- Pin the cap to the armhole from the center outward, matching the front and back notches and the underarm ends.
- Sew at the seam allowance: a straight stitch for wovens, with the sleeve underneath if there is a little ease; a narrow zigzag or stretch stitch for knits, at 1 cm (3/8 in) on Sewly knit patterns.
- Press the seam toward the sleeve on wovens; on knits, press it gently toward the body or leave it.
- Sew the side seam and underarm seam in one continuous line, matching the armhole seams exactly at the underarm.
Common mistakes and fixes
- Small pleats at the top of the cap. Too much ease landed in one spot. Unpick, redistribute and steam before sewing again, and make sure the seam runs between the two ease rows.
- The cap still will not fit. Some fabrics, especially polyester and densely woven cotton, cannot absorb much ease. For next time, lower the top of the cap by up to 1 cm (3/8 in) on the pattern, tapering to nothing at the notches, and check it on a toile.
- The sleeve twists forward or back. It is in the wrong armhole, or the notches were not matched. Swap the sleeves, double notch to the back.
- Diagonal drag lines from the cap. The cap height or sleeve angle does not suit your arm. That is a fitting question: test the sleeve in a toile and adjust there.
- The ease threads snap. Use a strong polyester thread in the bobbin, pull from both ends, and pull gently.
A woven top with short sleeves, such as the woven top / blouse pattern, is a good first set-in sleeve.