Broken thread, chewed fabric, plucked seam with overlock (serger) machine? Troubleshooting guide is here

UNDERSTANDING OVERLOCK (SERGER)

First things first - overlock machine and serger are different names for one machine - machine that trims and seals the edges of fabric. This machine is often used to clean seam allowance and prevent edges from fraying. Serger (overlock) seam has a good stretch and most activewear and swimsuits are sewn with it.

Below I will review and troubleshoot few main problems that are pretty common for serger machines.

PROBLEM # 1
SERGER MACHINE (OVERLOCK) SKIPS A STITCH.
There could be multiple reasons why your needle is not picking up a thread and skips a stitch. First, make sure you have a proper needle. When you are laying elastic over the fabric you are building up the thickness of stitched edge. Even though spandex is a rather light material you may want to switch to a larger needle for heavier fabrics due to elastic. Next, check your machine tension. There is no formula for tension as each machine is unique. The key here is balance in tension dials. Machine will not sew properly if dials aren't in tune with each other. However if your machine skips a stitch due to tension dials most of the time it is because one of them is too loose and releases thread too fast.

PROBLEM # 2
THREAD BREAKS.
Considering you have a high quality overlock thread most common reason for the thread to break is tension. Often times thread will break if dials are too tight and don't release the thread smoothly. Try pulling thread with your fingers IN and OUT of the dials, there shouldn't be much resistance. Too much resistance will break the thread.

PROBLEM # 3
MACHINES "CHEWS" FABRIC.
If this is happening when you are serging number one thing that can cause it is wrong threading. I would just remove all threads and run them again. Next thing to cause "chewing" is dull cutting blade. If the blade is not trimming fabric's edge clean you will be getting chunks of poorly trimmed fabric that will get in the way (or under the dog feed plate) and start pulling fabric in under your plate.

PROBLEM # 4
SEWN ELASTIC IS LOOKING TOO WAVY OR TOO SCRUNCHED
If your straps don't look flat but instead create waves or gathers the solution is simple - "feed" elastic to the machine with your hand. Sometimes you need to hold elastic creating small resistance so it doesn't go in too fast creating waves. Gathers will happen if your elastic doesn't go under the needle fast enough, for that you need to loosen the pressure foot and create a smoother path for elastic.