This is a fantastic way to finish a quilt that is meant for hard use, or one that is not intended as a show-stopping heirloom. It's great for pot holders! And, while I know there are a few people out there who can do this beautifully, it is not considered to be the nicest way to do the binding. The control you have with a traditional hand-sewn finish method will give a much better edge.
That said...let's look at how to do it!
Here are the supplies...I used a gold bobbin and black thread on top in hopes the pictures would be clearer (it's a usable pot holder!). The quilt block has one layer of cotton batting, and a backing made of blue terrycloth, and has been "quilted" (stitched through all layers) in a X. You can just stack the layers up and then trim them all to be the same size. I would also suggest that you do a quick zig-zag stitch all around the outside to hold the layers together better...not necessary for a regular quilt, though.
The binding is a French double fold , meaning the strip is cut and folded so the long raw edges are together. You may want to cut a slightly wider binding to finish by machine (2.5"). For a hand-finished binding, I cut it a bit narrower.
Sew the binding on the BACK, as it will be turned to the front. That is so the wonky stitching will show on the back, when it's done, not the front. Just sew it the way you usually do, folding and mitering the corners as you go around. Feel free to skip ahead here if you know how to sew a binding...
This is actually what I do (please do whatever works for you!). Sew towards the first corner, and stop 1/4" (OR the width of the seam allowance) before the corner. Remove the item from the machine, rotate to line up for the next side, and turn the binding strip up so the raw edge is straight in line with the side.
When you bring the binding back down to match the raw edges on this next side, the fold goes right at the top, even with the first side. I am using my fingers to keep everything in place...
...and I continue to use them to hold it all together. Feel free to pin, but I find it is easier to give it the "Pinch O' Death" to move back under the needle. If something slips, I can easily re-adjust it. Sometimes pinning and removing the pin will pull things out of place.
Eventually you get all the way around to where you started...and if you remembered to leave a bit unsewn, you can tuck the end inside the beginning. Or you can use any number of nice ways to sew the ends together...that is a subject all in itself!
Now turn to the front:
Pull all the binding to the front, and check a corner to see how the miter will fold. You are going to sew this the same way as any binding, so you want the first part to go smoothly down to the corner, then the miter forms when you turn the corner.
The difference is that you are going to topstitch right along the fold.Sewing close to the fold gives it a neat look....the fold should cover the bobbin thread (first line of stitching).
THINGS TO CONSIDER:
...Now the bobbin thread will show on the back, so maybe you want it to be the same color..
...You could match the fold to the stitching line, and in theory it would look like stitch-in-the-ditch along the back side (don't count on it!). There is a fusable thread, which you could use in the bobbin when you first sew the binding on, then you can fuse the fold right where you want it. And do remember to change it out before you go to the front.
...Matching the fold to the stitching line may not allow the edge of the item to fill the binding.
...You could use a fancy stitch with totally contrasting thread.
When we return to the back you will get the idea. Until then, let's keep sewing!
Sew all the way to the end of the side, at the corner. Backstitch, and remove from the machine.
Fold the miter in place, and continue topstitching along the fold.
There you are! Staying close to the fold keeps you from having a flap-like effect along edge.
So let's look at the back now (the bobbin thread is now red instead of gold):
OK, this is the important point...something is going to look funny, unless you happen to be one of those people who take the time to finesse the entire project. That means "be really fussy"...but thank-you if you are...you give the world something nicer to look at than my slap-dash style!
Now, it is possible to sew the binding on the front, as usual, and turn it to the back to sew down. Then you'd get this kind of stitching showing on the front.
OR you can sew to the front, turn to the back, but stitch-in-the-ditch along the front...and then you will get a flap on the back side, or not catch the fold evenly all around.
This is why Our Friend the Pot Holder is so good...he allows us to try out a technique so we can understand it, and then have a useful life in the kitchen! None of that wasted "practise time"!
A machine binding is a wonderful thing...but chances are it will not win you any Quilt Show ribbons, as some judges don't like it, even though (as I have shown) it is difficult to do nicely.
But it is very secure, and it is faster than a hand-finished binding, so it has its perfect place in the utility world....which includes a lot of great quilts for kids!