Lockstitch
A lockstitch is a type of machine stitching widely used for garment seaming and stitching, in which the top thread and bobbin thread are interlocked inside the textile to join pieces together.
Contents6 sections
Definition and Overview
Lockstitch is a sewing method that interlocks the top thread threaded through the needle and the bobbin thread in roughly the center of the textile. The stitches look relatively neat on both sides, and it is widely used for straight stitching in garment assembly, bags, and more.
In sewing processes, it is used for joining cut parts at the seam allowance, topstitching, attaching pockets, and more. Combined with the sewing order, seam finishing, and pressing open or to one side, it helps create the product's shape and strength.
Position in Product Making
Lockstitch is a basic process for assembling cut parts after cutting, based on the pattern and specification sheet. It manages seam allowance width, backstitching at the start and end of sewing, and stitch position, and connects to later processes such as pressing, attaching accessories, and inspection.
In process design, the thickness, stretch, number of layers, and whether there are curves in the textile are checked. On lightweight fabrics, seam puckering or gathering may occur, and on heavy fabrics, skipped stitches or thread breakage may occur at stepped areas, so conditions are determined through test sewing.
How to Proceed and Practical Points
When placing an order, specify in the specification sheet or sewing instruction sheet that lockstitch is to be used for each sewing location, along with the seam allowance width, how the topstitch should look, thread color, and whether backstitching is required. For visible topstitching, indicating the position and distance from the edge can reduce misunderstandings.
Before mass production, test sew using the actual outer fabric, auxiliary materials, interlining, and thread. It is important to match the thread tension, needle, presser foot, and feed amount to the fabric, and to check the right and wrong sides of the stitch, seam shrinkage, skipped stitches, and stitch stretch.
- Align the sewing direction with the grain and check for twisting or waviness.
- At intersections and stepped areas where thickness changes, check for needle breakage, skipped stitches, and stitch shifting.
- With stretch materials, check whether the seam will break during wear.
Quality and Ordering Notes
Lockstitch tends to produce stable stitches, but if the thread tension is improper, the top or bobbin thread may be pulled to the surface, affecting appearance and strength. Seam puckering, gathering, skipped stitches, thread breakage, and stitch slippage are subject to visual inspection and, if necessary, strength checks.
Because lockstitch alone cannot prevent the raw edge from fraying, overlock or similar finishing is used where seam finishing is needed. Also, for highly stretchable fabrics such as cut-and-sew knits, chain stitch may be selected depending on the application.
Differences from Similar Terms
Chain stitch is a sewing method that uses loopers to interlock thread in a chain. It is easier to obtain stretchability than with lockstitch, so it is used for knit hems and joining seams, but if the thread end comes undone, the stitch line may unravel continuously.
Overlock is a sewing method that sews while wrapping the raw edge with multiple threads, or that prevents fraying. The difference from lockstitch is that lockstitch mainly joins parts, while overlock is suited to finishing raw edges or sewing stretch materials.
Frequently Asked Questions
How do you choose between lockstitch and chain stitch?
In general, lockstitch is used for woven fabric seams and areas where you want to stabilize the shape. Chain stitch may be chosen for joining knit fabrics or finishing hems where stretch is needed. The decision is made through test sewing based on fabric stretch, the strength required of the seam, and the design.
How do you prevent puckering with lockstitch?
Puckering is more likely to occur when the thread is too thick for the outer fabric, the thread tension is too strong, or the feed amount does not match. Recheck the combination of fabric, thread, and needle, adjust the thread tension and presser foot pressure, and then test sew under the same conditions as mass production.
Does the seam allowance in lockstitch need overlock?
Because lockstitch does not wrap the raw edge, woven fabrics that fray easily often require separate finishing. In addition to overlock, methods such as French seams and flat-felled seams are available. Choose according to the fabric properties, feel against the skin, thickness, and wash durability.
