Anatomy of a Needle – More than meets the eye!

We Carry
by Sara Snuggerud in Sewing Tips

Written by Carol Meyer (Sara’s Mom)


I got new tires on my car the other day and it got me thinking how marvelous they are to move a very heavy automobile at high rates of speed. Then I started thinking about the needle in a sewing machine that also moves at very high rates of speed, and can sew faster than you can blink your eye.

While sewing machines themselves are wonderful pieces of machinery, the needle’s specific design makes the sewing process happen. Liken it to tires on a car if you will. No matter how well the car or sewing machine runs, the car won’t go anywhere without tires, and you won’t sew anything without a needle. But do we know anything about the way needles are made and what they actually do?

The first thing we all learn about needles is that there is a flat side on the top part and that the flat side faces towards the back when you insert the needle into the machine; remember “flat to the back”. You may have never looked any more closely at a needle than that except to thread it. However, there is more to it than meets the eye.


The stitch forming process has a lot to do with the machine and everything to do with the needle. If you have never noticed before there is a long groove the goes down the front of the needle. You can feel the groove by running your fingernail, or something sharp like the pointed part of a seam ripper, down the front of the needle. I’ll bet most of you never saw it or knew it was there.

When the needle goes down though the fabric, the thread lays into that groove. The size of the needle and thread must coordinate so the thread fits appropriately into the groove. If the needle is too small, or the thread is too thick, it will not fit into the groove and the stitches will not form correctly. You may even think there is a tension problem.

As the needle goes down into the bobbin case area there is a part there called a hook (I like to call it the “magic stitch maker”) that has a sharp point which moves around the bobbin area. When the needle is at the lowest position the point of the hook is right there to grab the thread from the needle. It is not until the needle starts to move upward with the thread nestled into the groove on the front side, that a loop is formed on the backside which the hook catches. The hook carries the thread completely around the bobbin case. The top thread and bobbin thread are twisted around each other and a stitch is made.

On the back side of the needle around the eye is an indentation called the scarf. The scarf allows the hook to get closer to the loop of thread. It gets so close to the needle that it almost touches; there is an infinitesimally small clearance between the two. If the needle is bent, even slightly, the hook could miss catching the loop, resulting in skipped stitches.

The diameter of the shaft of the needle determines the size, and the appropriate size should coordinate with the fabric and thread. There are two numbering systems for needle sizes, the American system (10, 12, 14, etc.) and the metric system (70, 80, 90, etc).  When the package says 80/12 it is referring to the same size of needle referencing both numbering systems. Which ever system you choose to remember is just numbers on a scale; the smaller the number the smaller the diameter of the needle, and the larger the number the larger the diameter. Size 80 or 12 is the middle size for average cotton fabric. Heavier fabrics use a larger size and lighter fabric can use a smaller size.

Home sewing machine needles will fit all brands of machines; however, not all needles are created equal. There are a number of minute differences in types of needles and point styles. Unless you have extremely good eyesight for seeing very small things you will not be able to see these differences without a microscope. Fine tooling makes some needles handle specialty threads better, or point styles that are specific for different types of fabrics.

It helps to have a system for knowing which kind of needle is in your machine. Some brands are color coded, but for the ones that aren’t you can color code them yourself with different colors of nail polish. A bit of color where the shank flares at the top coordinated with the same colored spot on the package is one way to know which needle is which after it is out of the package.

Where thread and fabric meet, it does not matter how much you paid for your sewing machine, if you do not use the right needle it will not sew well. Certainly if it is bent or broken you must replace it, but when you start a new project it is good time to start with a fresh needle. In terms of dollars, if you have spent $25 for fabric, thread and notions, spend $0.75 for a needle. If you have used five full bobbins for your project, which will be quite a lot of sewing, it is time again to put in a fresh needle. Like changing the tires on your car where the rubber meets the road, don’t wait until there isn’t any tread left to take care of the most important part of the journey.

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