How to Sew a Hem with a Twin Needle on a Regular Machine

A twin-needle hem gives handmade jersey garments a neat, ready-to-wear finish without needing an overlocker or coverstitch machine. Two parallel lines of stitching appear on the outside, while the bobbin thread forms a flexible zigzag underneath. This combination allows the hem to stretch as the garment is pulled on and worn.

The method works particularly well on T-shirts, knit dresses, leggings, sweatshirts and other garments made from stretch fabric. It can also be used on stable jersey, although the needle, thread, stitch length and tension may need small adjustments for a smooth result.

A little preparation makes a considerable difference. Twin-needle sewing is straightforward on a regular domestic machine, but testing on a scrap of the actual fabric helps prevent skipped stitches, tunnelling and wavy hems.

Choose The Right Needle And Thread

For most knit hems, use a twin stretch needle or twin jersey needle. The spacing is usually shown in millimetres, such as 2.5/75 or 4.0/75. The first number is the distance between the needles, while the second refers to needle size. A 2.5 mm twin needle creates a relatively narrow, subtle finish; a 4 mm version gives a more obvious double row.

A twin needle designed for stretch fabrics has a rounded point that helps pass between the fibres rather than cutting them. A universal twin needle may work on a stable knit, but it is more likely to produce skipped stitches on highly elastic fabric. Replace the needle if it becomes blunt, bent or damaged.

Use ordinary all-purpose polyester thread in both needle positions and in the bobbin. Polyester has enough strength and recovery for everyday knitwear. There is no need to wind a special bobbin thread, although a slightly lighter bobbin thread can sometimes make the underside less bulky.

Prepare The Hem Before Stitching

Finish the garment seams first, then decide how much fabric you want to turn up. A hem allowance between 2 and 4 cm is practical for many T-shirts and tops. Wider hems can be useful on heavier garments, while a narrow allowance often suits lightweight jersey.

Press the hem towards the wrong side using a low-to-medium temperature and a pressing cloth if the fabric is delicate. Avoid dragging the iron across the knit, as this can stretch the edge. Instead, lift and press in small sections. If the fabric curls, a narrow strip of lightweight fusible stay tape can stabilise the fold.

A useful alternative is to baste the hem by hand or secure it with a washable glue stick made for sewing. Pins placed at right angles to the edge can also work, but remove them before the presser foot reaches them. For a particularly curved hem, ease the fabric gently rather than forcing the fold to lie flat.

If your project includes a lined upper section, planning the hem finish alongside the lining prevents bulky layers from being caught accidentally; this lining a bodice neatly guide covers a related construction issue.

Set Up A Regular Sewing Machine

Insert the twin needle with the flat side facing the correct direction for your machine. Check the manual if you are unsure, because some machines require the needle to be positioned in a particular way. Select the straight-stitch setting and turn off automatic needle threading, as the twin needle will not pass through most threading systems safely.

Place one spool of thread on the normal spool pin and a second spool on an auxiliary pin. If your machine has only one spool pin, use a thread stand, a second bobbin positioned as a spool, or a small cup placed behind the machine. Both threads should unwind smoothly without catching.

Thread the first needle as usual, then thread the second needle separately. Keep the two threads apart until they reach the needle bar, and pass each thread through the correct needle eye from front to back. Thread the bobbin normally. Before sewing, turn the handwheel towards you to confirm that the needles pass cleanly through the presser foot opening.

Fabric or finish	Needle choice	Starting stitch length	Useful adjustment
Lightweight jersey	2.5/75 stretch twin needle	2.5 mm	Reduce presser-foot pressure if available
Medium T-shirt knit	3.0/75 or 4.0/75 stretch twin needle	2.5–3 mm	Use a narrow hem and gentle handling
Stable ponte	4.0/80 twin needle	3 mm	Lengthen the stitch if the hem feels stiff
Very elastic performance knit	Stretch twin needle	3–3.5 mm	Test carefully for skipped stitches
Decorative double row	Universal or stretch twin needle	3 mm	Check that the spacing suits the garment

Test The Stitch On Scraps

Use a piece of fabric containing the same seams, layers and hem allowance as the garment. Fold it exactly as the finished edge will be folded. Sew several centimetres, then stretch the sample across the direction the hem will need to move.

The top should show two evenly spaced rows. On the underside, the bobbin thread should pass from one needle line to the other in a relaxed zigzag. If the stitches break when the sample is stretched, try a stretch twin needle, a longer stitch length or a more suitable polyester thread.

Tunnelling happens when the fabric rises between the two needle lines. It is often caused by excessive tension, a narrow hem on unstable fabric or stitches packed too closely together. Lower the upper thread tension slightly, lengthen the stitch and add light stabilisation beneath the hem if necessary.

Skipped stitches can result from using the wrong needle, sewing too quickly or allowing the fabric to stretch as it enters the machine. Sew at a steady, moderate speed and support the fabric in front of and behind the needle without pulling it.

Sew The Double-Needle Hem

Place the garment right side up so you can guide the folded edge consistently. The inner needle should sew just inside the raw edge of the hem, while the outer needle remains a similar distance from the fold. If the seam allowance is wide, the twin needle may not cover the raw edge; trim or overlock the edge first if needed.

Lower the presser foot and take a few stitches by turning the handwheel before using the foot pedal. Hold the thread tails for the first few stitches so they do not tangle underneath. Sew slowly around the hem, checking every few centimetres that the fold remains flat and the fabric is not being stretched.

At the starting point, overlap the stitching by a short distance. Do not reverse unless your machine manual confirms that reversing with a twin needle is safe and the needle clearance is generous. Instead, leave thread tails, pull them to the underside and secure them with a small knot or several hand stitches.

When sewing a circular hem, keep the free arm clear of the rest of the garment. Rotate the project gradually rather than making sharp turns. If the hem has side seams or bulky intersections, reduce the speed and use the handwheel over the thickest areas.

Small Details That Improve The Finish

These practical habits help create a flatter, stronger hem:

• Use a stretch or jersey twin needle for fabrics with noticeable recovery.
• Choose a stitch length of roughly 2.5–3.5 mm rather than a very short stitch.
• Stabilise lightweight or curling jersey with narrow tape, tissue paper or temporary spray.
• Sew a sample after every major setting change, especially when adjusting tension.
• Press the completed hem lightly from the wrong side without flattening the raised double row.

If the fabric still ripples, allow the garment to rest flat after sewing and press it gently with steam held just above the surface. Some knits relax after washing, so laundering the sample can reveal whether the finish will remain stable.

A twin needle is also useful when a garment includes unusual openings or extra seam intersections. For example, a T-shirt with a gusset demands careful handling around changing seam directions; this practical T-shirt gusset guide explains how those construction details affect the sewing process.

Troubleshoot Common Problems

If the thread breaks at the needle, check that the thread is correctly seated in every guide and that the needle is fully inserted. The thread may also be catching on a rough spool edge or an incorrectly fitted spool cap. Re-thread both needle paths with the presser foot raised.

If the underside looks loose, increase the upper tension a small amount. If the fabric puckers or the double rows pull together, reduce the tension instead. Make one adjustment at a time, because changing several settings makes it difficult to identify the cause.

A hem that waves may have been stretched while sewing or may need stabilisation. Remove the stitches carefully, press the hem flat and try again with less handling. If the fabric has permanently stretched, trimming a small amount from the hem and refolding it may give a cleaner edge.

Regular cleaning also matters. Remove lint from around the feed dogs and bobbin area, particularly after sewing brushed or fluffy knits. Store spare twin needles in their packet so the points do not become damaged.

Once the stitching is balanced on a sample, sew the garment with confidence and let the machine do the work. A carefully prepared twin-needle hem can give a simple handmade T-shirt the polished finish of shop-bought knitwear. For site information and data-handling details, the privacy policy is available alongside the rest of the blog resources.