I think that many a seamstress becomes frustrated sewing with knits because they just don't have the right info and understanding about what they are working with. I love knits. Tiffany loves knits. And really they are not that difficult to use if you know a couple of things about them. Some we've already addressed.
Our absolutely #1 Tip and MUST do is
use a Ballpoint needle when sewing with knits.
Let me repeat that once more, use a BALLPOINT needle.
So what does "ballpoint" mean. This is going to be either a needle packaged as Jersey / Ballpoint or Stretch needle. Using one when sewing with knits will make your life so much happier. Based on the way the different needles are made (and I don't know the details) using a Universal needle on knits will actually cut holes in your fabric so that down the road you will start seeing little tears or runs at the seams of your garment. I know this from extended experience, before I knew using the right equipment (i.e. needles) can make such a difference. Ballpoint needles are designed so that they don't damage or break the knit fibers.
So last time...use a Ballpoint needle.
The slight differences between a Jersey needle and a Stretch needle, per the packaging, are that a Stretch needle is made "for elastic materials and highly elastic knitwear" (i.e. swimwear). It also says that it is "designed to prevent skipped stitches". A Jersey needle is "for use on knits and some stretch fabrics."
There is also a difference in price between a Jersey needle and a Stretch needle. Having just bought new needles to replenish my supply a 5 count pkg. of Jersey needles was $3.79 and a 5 count pkg. of Stretch needles was $5.49 at Jo-Ann's (before coupons).
Stretch needles are coded yellow--you can see this right below the portion of the needle that you position into your sewing machine.
I almost exclusively use a Schmetz Stretch Needle 130/705 H-S size 75/11, exactly as pictured above.
The Schmetz website has great info about needles and their uses. For as much sewing as I do with swimwear the Stretch needle is my better option. You wouldn't need it specifically for making t-shirts, unless you are having issues with skipped stitches.
The other needles you'll probably want to invest in down the road are some Stretch Twin needles. They come in either a 2,5/75 size of 4,0/75 size.
Unfortunately, I can only buy these needles at one store here locally, and it isn't Jo-Ann's. You will need to check your local fabric stores to see if they carry them. Remember it must say STRETCH. You can buy twin needles that are Universal, Metallic, Embroidery, or Jeans, but you must have a STRETCH twin when using it on knits.
A Twin needle is great of hemming (still allow some stretch) as well as great details on the collar/neckline to give your garment a more professional finish.
Next up we'll show you some different options for your shirts.