I agree, the answer really depends on the serger thread you are using. I would start by going to the manufacturer's website and looking to see what it actually is recommended for. That is a place to start. You can try breaking it just to see how much force it takes. Back in the day, I bought some of the "more economical" serger thread which was so easy to break. Nope, I would not use that. For my serger, I prefer to use regular quilting thread that the manufacturer says can also be used for serging. That way, I can keep less types of thread on hand.