How to use a Twin Needle
Twin needles come in two standard sizes.
A 4.0 twin needle is good for thicker or more stable knits, such as cotton spandex, French terry, and Ponte.
A 2.5 twin needle is great for thinner fabric like rayon spandex, brushed poly, and bamboo jersey.
Using a 4.0 needle on thinner fabric will cause tunneling between the two lines of stitching.
Before you install your twin needle, STOP and set your stitch to the centre straight stitch (01 on the picture below) Forgetting to do this is the easiest way to break your twin needle before you even start, because it will hit the foot.
Refer to your sewing machine manual to see how to thread your machine for a twin needle, as each machine may be slightly different. On most machines you will thread both spools the same, but the right thread you will not catch on the last metal hook before threading the needle.
Set your tension higher, to about 7 on a 1-9 scale. Your bobbin thread should zig zag between the top needle stitches which is what gives the straight stitch it’s stretch.
Lengthen your stitch for better results.
Stitch slow and careful, taking extra care as you go over seams. There is nothing more frustrating than breaking your brand new twin needle!