It's ok to machine bind. Or any other "rule breaking" quilting technique you want to do. It's ok. I used to be a bit ashamed that I don't hand bind, but I'm letting go of that.
My crafting philosophy is about how to get the most done with the least time/effort. I like short cuts. I'm ok with that. If I were to hand bind my quilts like you are "supposed to" I would have precisely 0 quilts completed, rather than dozens. I have come a long, long way in machine binding and have finally developed this method after tons of practice and experimenting.
This tutorial is going to assume nothing about your quilting skills, please excuse any simplicity in the interest of full clarity. And, actually, if you want to hand bind, just follow the tutorial up until the last step (and also attach your binding to the front, rather than the back).
2 1/2 inch strips of fabric to equal the perimeter of your quilt sandwich plus about 12 inches (more for seaming)
1/4 inch foot for your machine (not a total necessity, but it's nice!)
To start with we'll do a little math and cut our binding strips. My quilt sandwich for this project was 19 inches square. 19 x 4 =76
76 + 12 =88
WOF (width of fabric) is about 42-44, let's say error on the lower side and then say 41 after cutting the selvedge off. So, to hit 88 inches we'll need 2 strips of fabric. I went nuts and decided to do 2 1/2.
1.) Cut your fabric strips 2 1/2 inches wide. I fold my fabrics selvedge to selvedge, and then once again and slice off the end through 4 layers. You need to be careful doing this so it's not crooked, but it's another one of my shortcuts/something I don't do "exactly right."
2.) Once you have your strips, piece them together on a diagonal. A diagonal seam will help the bulk be spread out in the final binding, rather than all on top of each other making a thick spot that looks weird and is tough to sew over.
Lay 2 strips right side together perpendicularly to each other, and pin on both sides as in the picture. With a pencil and ruler, draw a diagonal line from corner to corner.
Using a standard foot, stitch along the line and cut off the excess fabric, leaving a 1/4 seam allowance or so.
Press the joining seams open.
3.) Press your binding. Fold in half, wrong sides together, and press, using some steam if you like (I like).
Yay, pretty binding!
4.) Now we'll attach it to the backside of your quilt sandwich. That's right, the back. Usually when binding you start on the front. Start by changing to your 1/4 inch foot, if using one.
Pin your binding to the back of the quilt sandwich. With one pin, it's the only pin we're going to use. Pick the middle or right side of any one side of your quilt sandwich and pin the binding. Leave about 6-8 inches of binding dangling, we'll use that later. The raw edge of your binding should align with the raw edge of your quilt sandwich.
5.) Begin to stitch, using a 1/4 inch seam. I use my 1/4 inch foot for this, again, because it's easy and consistent. Back stitch whenever you start and stop in the following directions. Stitch until you are 1/4 inch from the first corner.
Back stitch and pull the work out. You may cut the thread or let it dangle, whichever you prefer.
Now we are going to fold to create the mitered corners. Fold the binding to your right, creating a diagonal crease. Sadly my fingers are kind of in the way so you can't see the fold very well, but you can see the angle that I folded the binding.
Now, holding that first diagonal fold in place, fold the binding straight down, so it is now parallel with the next side we will be sewing.
Rotate your work as we are now sewing a new side and carefully ease the folded binding back into your machine. Starting at the very edge (not 1/4 inch in like when we stopped sewing), begin sewing and go ahead and back stitch.
6.) Continue stitching all sides and work each corner as described above. When you round the fourth corner*, stitch a couple of inches on the new side (the side you started on), back stitch, and remove from the machine. Now we are going to connect the binding beginning to the end.
*This is a small quilt, if you're working on a big one then maybe you want to stitch halfway down the side or more, usually having 1-2 feet of working space is ideal. More than that and your binding might be too loose, less than that and it's a nightmare to sew together.
7.) Usually we're told to overlap the ends of the binding as much as their original width. I've found that that makes my binding a little bit too loose, so I subtract 1/4 inch from that. Since we started with 2 1/2 inch wide binding, we want to overlap 2 1/4 inches. Lay a ruler on top of the dangling binding from the beginning (remember how we left a piece unstitched before our first and only pin?) and the piece you rounded the corner with. Overlap them 2 1/4 inches and cut off any tails. If you center this as well as you can it will be easier for the next step.
8.) Attach the ends of the binding together. (You might need to switch back to your regular foot for this step, I always do). To do this, you want to open up the binding and put the two pieces right sides together in the same perpendicular manner as we did earlier. The more room you have to do this, the easier, so if you have several inches of not stitched down binding on each side, all the better (this is why we left the binding dangling at the beginning and stopped stitching soon after we came around that final corner).
Pin, draw your diagonal line, and stitch as before. Before cutting your seam allowance however, be sure to fold the binding back together, just to make sure you've stitched correctly. I can't tell you how many times I stitched on the wrong diagonal or had the binding twisted. As long as you haven't cut off the excess seam allowance yet, it's not too hard to rip out your stitches and start again.
Ok, once you know you're good you can trim and iron the seam allowance, and then iron the seam in your binding fold again since it's probably a little messed up.
9.) Finish sewing the last side of your binding. Back Stitch. Yay, your binding is now attached and you have done a continuous binding! Go ahead and switch back to your regular foot, we're done with the 1/4 inch foot now.
10.) This step insures a crisp fold and an even amount of binding showing on the front side. Take the folded side of the binding and fold it again, a parallel fold, so that the original fold lines up on top of the raw edges. We're going to iron this on all four sides. Don't get too close to the corners, leave them alone for now.
11.) Go ahead and flip your quilt over to the right side. We're going to machine sew the binding to the front now, using the regular foot for your machine. I would advise changing to a color of thread that closely matches the color of your binding if you want it to blend in. I usually do so, but didn't this time. Starting in the middle of one side, fold the binding over to the right side of the quilt. The fold we just created with the iron will line up with the edge of the quilt and fit snugly.
12.) We're going to begin stitching slowly and very, very closely to the edge of the binding fold. If your machine has a speed regulator, I recommend slowing it down. Begin stitching 2 needle widths or so from the edge of the fold of the binding (maybe a millimeter? If you're very far away from the edge it will stick up and not look good). Only take 1 or 2 backstitches as you begin. Like I said, pins aren't needed. Just fold a few inches over at a time, going slowly, and stitch them down. The folded binding will easily cover the 1/4 inch stitch line we used attaching the binding.
13.) When you get a few inches away from the corner, fold and smooth the next side down a few inches from the corner (the binding that is currently horizontal to your machine). Use your finger to fold all the way to the corner. When you get to the corner, fold your current side (the side your are currently stitching) down. Hold the corner in place as you stitch to the corner. (the next 4 pictures probably show this better than words)
Stop with your needle down in the corner, raise your presser foot, and pivot the work beneath you. Sew the new sides, slowly and carefully until you get to the next corner and proceed as above. When you get back to your starting place, backstitch just two or three times. Carefully cut your thread ends. Do a little binding dance, because you're done, baby!