How to Sew a Double Needle Hem for Knit Fabrics
Knit fabrics have transformed home sewing, with stretch cotton, jersey, and interlock lining the shelves of fabric stores from Brisbane to Perth. A double needle, often called a twin needle, creates two parallel rows of stitching on the right side of the garment while a soft zigzag forms on the underside. The result is a hem that stretches with the fabric, mimicking the look of a commercial coverstitch machine.
Many Australian sewists first discover the technique while upcycling op-shop finds, where a favourite t-shirt or knit dress has lost its original hem finish. A twin needle offers a budget-friendly way to restore that professional appearance without the cost of a dedicated coverstitcher, which can retail for over $2,000 AUD. Hobbyists and experienced makers alike benefit from mastering this method.
The process is straightforward, but careful preparation of tension, needle spacing, and fabric handling is what produces crisp, even lines. With the right setup, a single hem on lightweight jersey can be completed in well under ten minutes, making it practical for wardrobe staples and larger projects.
This guide walks through every stage, from selecting the correct needle to troubleshooting skipped stitches. The aim is a finish that looks polished, feels comfortable against the skin, and holds up to repeated wear and washing in Australian conditions, where summer heat and coastal air stress seams.
| Method | Equipment needed | Stretch recovery | Cost (AUD) | Best for |
|---|---|---|---|---|
| Twin needle hem | Standard machine, twin needle, knit foot | Good | $5–$15 | T-shirts, jersey dresses |
| Coverstitch | Dedicated coverstitch machine | Excellent | $2,000–$4,500 | Production, activewear |
| Narrow zigzag | Standard machine, single needle | Very good | $0 | Quick fixes, stretch seams |
| Serger rolled hem | Overlocker | Good | Owned | Lightweight knits, edges |
| Blind hem stretch | Standard machine, blind hem foot | Moderate | $15–$25 | Trousers, stable knits |
Tools and materials you'll need
A twin needle is the centrepiece, and Australian fabric retailers such as Spotlight, Lincraft, and The Remnant Warehouse typically stock sizes with 2.5 mm and 4.0 mm spacings. For most jersey hems, 2.5 mm gives a subtle finish suitable for t-shirts and tops, while 4.0 mm works well on heavier ponte or French terry. Ballpoint needles in sizes 75/11 or 80/12 glide between knit loops without piercing them.
A second spool pin is required to thread the twin needle. Most modern machines, including Husqvarna Viking, Brother, and Janome models sold through Australian dealers, include a spare pin in the accessories box. Other essentials are a knit foot, polyester thread, wooly nylon for the bobbin, scissors, a tape measure, and a water-soluble marker. Wooly nylon in the bobbin keeps the underside elastic on slippery viscose jerseys.
Preparing your knit fabric
Pre-washing the fabric should never be skipped, particularly with knits that may shrink on the first wash. Australian-made jerseys from Clothedit or Knitwit often arrive pre-shrunk, but imports from Adelaide's Hettie's Patch or Melbourne's Tessuti still benefit from a gentle cycle and flat drying. A fabric that shifts will produce a wavy hem no matter how carefully the stitching was applied.
Cutting the hem allowance depends on the garment and the desired finish. For t-shirts and casual tops, a 2.5 cm allowance is standard, while longer tunic hems may use 3 to 4 cm. Folding the allowance up by half, pressing lightly, then folding again creates a clean double-fold hem that encloses the raw edge. Pressing with a low-heat iron and a pressing cloth prevents shine on dark knits and protects elastane fibres.
Pin or clip the hem in place every 5 to 8 cm, paying attention to the grainline. Knits have a tendency to stretch sideways as they are handled, so measuring the hem depth at several points and adjusting for unevenness before stitching saves time. Clover clips from Australian quilt shops hold the layers without distorting them.
Setting up your sewing machine
Inserting a twin needle requires care because the two needles share a single shank. The flat side of the shank should face the back of the machine, matching the orientation indicated in the user manual. Once seated, thread each needle separately, ensuring the two threads pass through separate tension discs when the machine offers a twin-needle setting. That setting prevents tangling and reduces needle breakage.
Tension adjustments differ from standard stitching. Most machines run with the upper tension slightly looser than usual, often dropping from 4 to around 2.5 or 3. A test sample on a scrap of the same fabric is essential before approaching the actual garment, since settings that look correct on woven cotton behave differently on stretch knits. Stitch length typically sits between 2.5 and 3 mm.
The stitch selection should remain on straight stitch, as the twin needle itself creates the zigzag on the reverse through the bobbin thread looping between the two needle threads. Switching to a stretch stitch on most domestic machines interferes with this function and may cause skipped stitches or thread nests underneath.
Testing the stitch on scrap fabric
Scrap testing is non-negotiable, even for experienced sewists. Cut a piece of the project fabric at least 30 cm long and 20 cm wide, fold and press a hem, and run a test seam. Examine both sides: the right side should show two perfectly parallel lines, while the underside should display a flat, even zigzag loop that pulls slightly without breaking.
Adjust the tension incrementally if the bobbin thread pulls through to the right side or if needle threads bunch on the underside. Small quarter-turn changes make a difference, saving hours of unpicking later. Local sewing groups, such as those at Brisbane's Reverse Garbage or Sydney's Sew Make Create, often host troubleshooting sessions where beginners can compare notes.
Sewing the double needle hem
Place the fabric under the presser foot with the raw edge aligned to the correct seam guide on the needle plate. Many Australian machines use a 1.5 cm guide line etched into the metal, though attaching a strip of masking tape offers more flexibility for wider hems. Sew slowly, keeping the fabric edge flush with the guide without pulling or pushing, since knits stretch easily under tension.
Pause every 15 to 20 cm to check that layers feed evenly. If one side begins to ripple, stop, redistribute the fabric, and resume. Reverse stitches at the seam end are optional on knits because the zigzag loop already secures the threads. Trim the loose tails once the seam is complete.
A final light pressing completes the project. A damp pressing cloth and a warm iron set to the wool setting work well for most cotton and viscose knits, while synthetic blends require a cooler temperature. Avoid dragging the iron, which can distort the parallel stitching lines.
Troubleshooting common issues
Skipped stitches usually indicate the wrong needle type or one that has become blunt. Ballpoint needles wear out faster than universal needles, especially on heavier ponte or interlock, so replacing them every two to three garments is wise. Australian service centres in most capital cities can test needles and recommend suitable replacements.
Puckering along the stitch line often traces back to excessive upper tension or a presser foot pressure setting that is too heavy. Loosening the upper tension by half a turn, and reducing presser foot pressure if possible, usually resolves the issue. Lightweight tear-away interfacing beneath the hem can stabilise particularly stretchy knits during stitching.
When the two rows of stitching appear uneven in length or spacing, the most common cause is a bent twin needle. Even a slightly damaged needle produces visible distortion, and replacement is the only reliable fix. A small stash, perhaps ordered from Spotlight's online store, avoids project delays.