What do the numbers mean?
Quilting--and sewing in general--is full of numbers. Piecing measurements, thread weights, needle sizes. Numbers everywhere!
There are two systems for numbering sewing machine needle sizes. The European system numbers range from 60 to 110 and the American system numbers range from 8 to 18. Those two numbers generally appear on sewing machine needles separated by a slash: 70/10, 80/12, 90/14. In both systems, the larger the number, the larger or thicker the needle. This is the opposite of thread weight, where the larger the number, the finer the thread.
What happens if I use the wrong size needle?
A host of problems can arise if your needle size is out of sync with the needs of your project. A needle that is too thin will bend or break easily, skip stitches, have top thread tension problems, or create thread nests on the back of your sewing. A needle that is too thick will leave large, noticeable holes in your fabric and can create tension issues that result in wrinkly stitch lines.
What size needle do I need for my project?
The size numbers correspond to the thickness of the fabric you can safely sew without risking the needle bending or breaking due to the fabric weight. I sew most of the time with an 80/12 or 90/14 needle, but occasionally I need a 70/10 for finer work.
Fine: light silk, organza, tulle, fine lace, chiffon
Lightweight: synthetics, spandex, lycra, cotton voile, silk, quilt cotton
Medium weight: quilt cotton, velvet, fine corduroy, linen, muslin, jersey, tricot, knits, light wool, sweatshirt knit, fleece
Heavyweight: denim, corduroy, canvas, duck, suiting, leather
Very heavy: Heavy denim, heavy canvas, upholstery fabric, faux fur
Extra-heavy: Industrial heavy fabrics. Many home machines would struggle to power through this kind of fabric, so a 120/20 needle would be relatively rare in a domestic sewing machine.
Are there different needle types, as well as sizes?
Yes! Different types of needles have slight variations in the way they're constructed, which in turn affects the needles that will work best for different types of projects.
Universal Needles: The most common type of needle is a universal needle. It's probably what came with your sewing machine when you bought it, and it'll work for most common sewing projects. It has a slightly rounded tip, and it will sew beautifully through all kinds of natural and synthetic fibers. You can also get universal needles with a nonstick finish that will allow you to sew through adhesives and fusible with minimal retention or buildup of adhesive material.
Ball Point or Jersey Needles: This needle with a rounded tip goes cleanly into the fabric fibers without cutting through them and forming needle holes. They can be used for knit fabrics, cotton, polyester, and poly-cotton. They work particularly well with T-shirt knits which have a fairly low stretch factor.
Quilting Needles: These needles are strengthened for use with the multiple layers of a quilt sandwich. They're also good for making bags or items where you're sewing through interfacing or thick layers.
Topstitch Needles: These strong needles have large eyes for use with thick threads used in decorative topstitching.
Sharp/Microtex Needles: Sharps are both finer and sharper than a universal needle and usually they're strengthened as well. They can easily sew through vinyl, applique, and tightly woven fabrics.
Denim Needles: I've never sewn a pair of jeans from scratch, but if I did, this would be the needle to use. They are both strong and thick to handle multiple layers of denim or heavy canvas. I have done denim repairs with a heavyweight universal needle rather than a denim needle; use gentle speed and work carefully.
How long should my needles last?
Needles aren't made to last forever. I generally get about 8-10 hours of sewing--not time in the sewing room; actual hours that the machine is running--per needle. The easiest way to tell if your needle needs to be changed is to listen. If you hear any kind of soft popping sound as the needle enters the fabric, that's a sign that the needle is dulling and is due for a change. You might also be experiencing shredded or broken threads, skipped stitches, puckered fabrics, damaged fabrics, or uneven seams. These problems can all stem from wear on your needle. You won't be able to see or feel the striations and burrs that form on a worn needle, but your thread and your fabric can. If you're experiencing thread shredding and your needle is new, it's rare but possible to have a burr in the hole of the needle from the manufacturing process. To test, floss a fragile thread--metallics are especially good for this--quickly back and forth through the needle angling it on all sides of the hole. If your thread shreds or gets flyaway fibers, toss that needle.
Pro tip: When you change your needle, you should also unscrew your stitch plate and clean out any accumulated lint. You're not trying to make your own felt in there, and excessive lint buildup is a machine killer.
Are titanium-coated needles always better?
As with many sewing questions, this is a matter of personal preference. Titanium needles are stronger and will last longer than standard needles because they resist abrasion via their titanium-nitride coating. For this reason, they're more expensive than non-titanium needles. However, when they break, they have a much higher potential to damage your machine and/or your person. I choose not to use titanium needles in either my domestic machine or my longarm. I don't want to risk an expensive repair, and it's about the same cost to use a less expensive needle and change it a little more often.