Lock stitches are sewn either by a machine or by hand, and both sewing techniques yield the same stitch in sturdiness and appearance. A machine created lock stitch uses two threads -- one on the top and one on the bottom -- and a handmade lock stitch uses only one thread.
Purpose
Lock stitches are common across a range of industries from seamstresses to leather makers because the stitch is sturdy enough to hold if one section becomes unraveled. Lock stitches are common in clothing because it withstands consistent wear and washing, and if one thread breaks, the hem’s strength is not compromised and the break will likely go unnoticed. Some convertible car covers also have lock stitches because the covers are constantly getting wind-whipped and if one stitched section comes loose, the car cover will keep its shape even during a long drive.
Machine Lock Stitch
A lock stitch is a standard sewing machines technique that uses two threads -- one held by the bobbin and the other by the needle -- to create a tightly bound stitch. A sewing machine wraps the two threads around each other at set intervals. Some sewing machine settings show the stitch outcome appearance instead of the name of the stitch, so review the sewing machine’s manual to see its required setting for a lock stitch. Hobby sewing machines create lock stitches quickly in many thin fabrics, but their needles are typically not strong enough to pierce thick leather.
Hand Lock Stitch
A sewing awl allows you to create a lock stitch by hand using one thread. This tool has a thick, strong needle for piercing leather and other thick fabric when a sewing machine is not capable. Another difference between using an awl and a sewing machine is that you predetermine the amount of thread you need for the project on an awl before making the first stitch. The first stitch starts at the thread’s center so you do not have loose thread ends, similar to using a sewing machine, where you begin the first stitch.
Considerations
A sewing awl is better than a sewing machine to repair previous lock stitches because you have more control over the needle, allowing you to use the previously created stitch holes. Consider waxed floss, which typically comes with the purchase of a sewing awl, for repairing leather goods because waxed thread holds its shape. Tie off the end by cutting the thread from the awl when both thread ends are on one side of the fabric. Use a couple square knots to secure the thread in place.
