At one time I thought you could use the same sewing needle until it bent or broke, and while you can, it does not give you the best stitching results. It is important to change your sewing needle to keep a fresh point, and also to use the correct size for the fabric you are sewing. Below, I will take the mystery out of which sewing needle to use for the best results.
There are 2 systems for needle sizes:
European system ranges from 60 to 120
American system ranges from 8 to 20
Both sizes systems are listed on the needle packaging, such as, 70/10, 80/12, etc.
Quick Needle Guide:
60/8, 65/9, 70/10: Very Fine Silks, Fine Lace, Organza, Chiffon, Voile
70/10, 80/12: Cottons, Cotton Blends, Synthetics, Silks, Knits, Jerseys
90/14, 100/16: Denim, canvas or heavy interior fabric
For knits, I have had the most success when using a Jersey needle or Stretch needle, they have created the point of the needle to smoothly go through the weave of the fabric.
There are now many specialty needles beyond the size, if using a denim or jean thread, switch to a Topstitch needle, the hole is made larger so the thread can pass through easily. The same is for the Metallic threads, there are Metallic needles designed to accommodate the thread so it does not break as it is passing through the needle.
The recommendation for changing a needle varies from every 4 - 8 hours of sewing time, or after you have used 3 bobbins of thread.
When needles become dull or bent (even so subtle you don’t notice), you may get skipped stitches, broken or looped thread, runs and pulls in the fabric, or even damage to your machine.