First of all, WOW. Lot's of new folks since I've spent anytime here. In reading through some recent posts, lots of sewing questions. I thought I would add to or consolidate the great info in the posts based on my experience.
Pin vs fold and sew.
-Fold and sew. Pinning takes too long. You'll be glad you developed this skill. The tricky part for new folks is keeping the fabric even. Just pay attention and fold it over and sew it instead of stretching it where the ends come out uneven.
-Don't watch the needle, watch the material at the front of the machine (or at a minimum, at the front of the needle plate). Once it's lined up there, it will line up at the needle with a little minor steering.
-Learn to sew fast. Most find it easier to sew a straight line while sewing faster rather than slower.
-Don't worry about not having perfect seams. Only you will notice and people that photograph their recent "creation" for posting, usually don't photograph the bad spots.
Binders, hemmer attachments, hemmer feet.
I use them all and love them.
-Binders work like a champ almost always. Worth the money for a cheap one if you make tarps. Next time I bind a tarp, I'll post a video. You'll buy one instead of trying hem silnylon or bind freehand.
-Clean finish hemmer attachments (double fold, roll hem or whatever) take practice but work pretty well on nylon. I typically do a 10' seam with a hemmer in 45 sec to 1 minute. I usually have one or two screw ups per hammock that I might fix, but still pretty fast and I don't have to worry about the ends coming out even.
Here is a quick video I just shot with my left hand and trying to steer the fabric with my right while watching the screen on the camera. This is in nylon taffeta. It works about the same in 1.7 ripstop and worse in 1.1 sil. Don't judge the hemmer solely by this because I could not control how much fabric was going into the hemmer. But even 1 handed and not looking, it did pretty good until the very end when I let too much fabric into it. The machine is my "newish" Bernina 217N-8. Sweet.
-Hemmer feet. These work better than the hemmer attachements for small hems (1/8"). Not quite as finicky, especially in zigzag and letting the hem roll up into a rolled/round hem. Usually once it's started, I "floor it" with the pedal and run about 4500 stitches per minute. Comments on hem size below.
Most use about 1/2" because it's easy to fold. I don't believe there is any real magic. I don't see why a 1/16" or 1/8" hem would not be just as strong, just WAY harder to fold. I say that to say if you have a small hemmer foot, try it out.
Sewing machine problems.
-When you have a problem, change the needle and rethread. While your rethreading, take a minute to check the tension disks and bobbin case (if you can see them) for lint.
-I believe 90% of sewing problems are needle or tension related. Many tension problems are incorrectly threading the machine or lint that holds tension disks open.
-The normal tension check is the location of the knot in each stitch (should be centered in the fabric, knot not visible from top or bottom). Knot on top, reduce top tension. Knot on bottom, increase top tension.
-Adjust ONE thing at a time.
-Occassional loops up top mixed in with good stitches indicates too little bobbin tension.
-Lots of loops on the bottom leads to thread breakage. This usually means your tension disks up top are not working at all. Machine is threaded incorrectly, lint in top disks, or you forgot to put the foot down.
-Thread breakage as speed increases usually indicates a needle problem. Possibly several others. Change needles first, then try changing to a bigger size if it keeps happening. Check for too much top tension next.
-Needle Breakage - lots of reasons for this, but usually its too small of a needle. Another common cause is the fabric is moving while the needle is engaged in the fabric. Either you need to stop pulling the fabric (common) or increase presser foot pressure.
-I wouldn't start suspecting timing unless the machine has never worked correctly or you've done something to change the timing. Sewing too heavy a material (denim seams or larger) or needle strikes can knock the timing out, but it's uncommon.
-Another problem with poor stitch quality is presser foot tension. You only need enough to move the fabric, but slippery fabrics like sil are very tricky. Too little and it slips ->uneven stitch lengths. Too much and the bottom feeds more than the top->ends don't match and you get odd humps of fabric.
If you have a tension problem, start with the top tension in the middle and sew something easier to sew than ripstop or sil. Think old shorts or dress shirts. Nothing stretchy like a t shirt.
-Buy older vs newer.
-The more metal the better. All metal gears are the best. Avoid electronic, if your buying one new for just gear.
-If you think you'll do this for a while and have a little $$, buy an true industrial sewing machine off craigslist or yard sales, mounted in a table with the motor underneath. Plenty of great machines for $200-$300.
-Another industrial type machine may have the term "Artisan", "Professional", or "Commerical". Not true industrial, but VERY good. Just do your research. Singer 20U, Bernina 217, Pfaff 138 are all good Artisan grade zigzag machines.
-"Industrial strength" is a sales term used on ebay. Ignore it, but it might indicate a metal gear machine. Most true industrial machines are usually very, very fast and do one thing only. They are made to run 24/7 at high speed. Industrial does not neccessarily mean strong. Strong machines are sometimes called upholstery machines.
-Learn how to fix them, especially the older ones. Remember, we're men (most of us), doing manly things, like making gear so that we can go make fire. If you're not afraid to pop the hood on your truck, don't be afraid to take apart a sewing machine and at least look inside, clean it and oil it. There are a lot of free or inexpensive tuning manuals available online.
Sorry for the long post. Hope it helps.