Shank-The top part of the needle that goes into your machine. Home-sewing machine needles have a flat back that corresponds with the machine, so it's easy to fit the needle into the machine at the right angle.
Shaft-The main part of the needle below the shank.
Front groove-The slit on the front of the needle. This is where the thread sits while sewing which protects it from breaking.
Scarf-The skinny space in the back of the needle which helps the machine not skip stitches. The scarf is actually longer on stretch needles to accommodate the fabric.
Eye-Just like a hand-sewing needle, the eye is the hole where the thread goes. The difference is sewing machine needles is that the eye is on the opposite side of the needle.
KINDS OF NEEDLES
Universal needles-Like the name says, it's universal and can be used for almost anything. The point is sharp with a little bit of rounding. It can't be seen with the naked eye, so I included a picture with examples.
Ballpoint needles-The point is very round and is for knit fabric. When sewing with knit fabric, you don't want to pierce the fabric like you do with woven fabric. You want to push the yarns aside. If a yarn is broken in knit, it unravels.
Stretch needles-Similar to a ballpoint needle, it just has a deeper scarf to prevent skipped stitches.
Sharp needles-Sharper than a universal, this needle is used for wovens, fast straight-stitch sewing (like quilting), and topstitching. It makes a clean stitch because it is so sharp.
Jean needles-Thick, sharp needles to accommodate thick fabric.
Leather needles-Sharp needles made specifically for sewing on leather. I have never actually sewn on leather, so I don't know much about it.
Twin needles-Two needles connected at the top so it can be put in the machine as one. When sewing, the stitching on top is two parallel stitches with a zigzag on the bottom. The zigzag comes from the bobbin thread going back and forth between the two needles. There are also stretch twin needles for sewing on knits and jean twin needles for making that common double thread we see on jeans these days.
The European needle measurement is first, and the American needle measurement is second.
Very lightweight 70/10
medium weight 90/14
medium to heavy weight 100/16
heavy weight 110/18
The size I use for almost everything is 80/12. When I'm sewing on jeans or thick fabric, I use 100/16 or 110/18. I would use the 70/10 for sheer fabrics.
Also, the smaller the needle, the thinner the thread size has to be so that it can fit into the front groove. The larger needles can accommodate thick thread. They won't work as well with thin thread because the thread will flop around inside the front groove because the groove is too big.
Regulation length 2.5 mm long (10-12 stitches per inch)- I use this stitch length for everything I do.
Topstitching length 3-4 mm long (6-8 stitches per inch)- I have never used this length and didn't even know there was such a thing. I do lengthen my stitch when I'm tailoring jeans if I'm trying to match the previous stitching.
Basting/gathering length 4 mm long (8 stitches per inch)-Basting is a helpful stitch as is gathering. I will be doing a future post in this.
Reinforcement stitching 1.5 mm long (15-20 stitches per inch)-This length is for strength. I use it when sewing on loosely woven fabric with corners that are going to be trimmed.
Here's an assortment of Universal Needles (affiliate link) to add to your collection!