WillGeorge, An Overlock is also called a serger. It is known for cutting and sewing at the same time. It typically uses 3 and 4 spools of thread at a time. This being said, most often the thread for these machines isn't as strong, and a lot of times is not appropriate for use in your utility sewing machine.

A lot of needles are packaged with recommendations for use on certain fabrics and threads. The staff at a lot of fabric stores can be very helpful in matching your project, with appropriate fabric, thread, and needles.

LindaJCasey, I agree with your assesment on thread. I do more garment sewing, and try to match thread content with fabric content. Silk thread has been known to cut fabric at times as well.

I do have a question to the author of this article, If the thread is properly chosen for the fabric, and the needle is properly chosen for the fabric weight and content, will It not also be right for the thread? With the exception of embroidery and metelic?
Perhaps I have been lucky so far, but I have found so far that matching everything up this way has worked. Is there a test to determine that your thread and needle are made for each other?