Sewing machine needles have become more sophisticated over the years because of new sewing threads and novel fabrics becoming available in the marketplace. Needles are found in various sizes, with different shapes and attributes to suit different materials and applications, and with more than one needle on a single crossbar for multiple stitching.
Needles range in thickness, or size, from very fine 60/8 to a heavy duty needle 120/19 - the most common “middle-of-the-road” size selected for standard needles is 80/12.
Most needles use the two number measuring system. The higher number (e.g. 80) relates to the metric system used in many countries including Australia, and it defines the needle shaft diameter in fractions of a millimeter. The lower number (e.g. 12) relates to the measurement system used in the U.S.
Conventional sewing machine needles are standardised by manufacturers, but not so with overlocker needles. There are more than 10 needle systems available for overlockers. Always consult your overlocker machine manual when replenishing your needle supply.
An overlocker may take a special needle such as an industrial needle with a flat or round shank. Other overlockers may use standard Universal machine needles with sizes 75/11 or 80/12. Either way, when changing needles, test the stitch formation by manually turning the wheel to be sure the loopers and needles interact properly. When two needles are used with the overlocker, the needles are set at slightly different heights. This is the correct configuration. Check your manual to be sure the right needle is supposed to be lower than the left needle on a 2-thread overlocker. This height difference is due to the rising arc of the upper looper as it comes up and over the fabric.