Some machines are much easier to thread than others. Some sergers use industrial needles instead of conventional sewing machine needles. These needles are available in various sizes for sewing on different weights of fabric. These needles have a round shank, so you must be careful to insert them correctly with the long groove in the front and the scarf in the back. If you insert the needle incorrectly, stitches do not form properly.
Some sergers use conventional sewing machine needles.
These needles are easy to insert, since one side of the needle is flat at the top and fits into the machine only in one direction. Each thread on the machine has a tension dial it must go through to control thread movement. Tension dials are located on the inside, outside, or set into the machine. Most are numbered or color coded to help gauge tension. On most sergers, you can vary the stitch length and width settings, and adjustment depends on the brand of machine.