Cutting Bias Binding
One of my pet peeves is cutting bias strips for binding out of squares. Unless you are lucky, the square is never exactly the width of the fabric, so you have a leftover hanger-on piece. And I can never cut straight with the stitched up tube. Or, if you cut straight from yardage, you have a giant triangle hanger-on piece making a mess of the remaining useable yardage. I prefer to use bias binding. And I use my walking foot to stitch it to my quilt, straight or curved.
I need to cut binding for this one. I finished the hand quilting, and I measured for binding. I have calculated that I'll need 215 inches roughly. I want to add 10 inches for joins and corners (a figure pulled out of thin air... no particular reason for 10). The nifty bias-out-of-squares chart isn't helping me out a lot here, so there must be a better way.
Bias is always the hypotenuse of the right triangle created by warp and weft, so math will be my friend:
So... I used this nifty formula to calculate just how many 2.5" strips I can get out of a width of fabric. Formula says: 11.4 strips. (The calculations on this are not going to make sense without using superscript font, so take my word for it :o) Take your total inches required, and divide by 11 (because that 0.4 strips is going in the crumbs bin, not on the binding). This is how many strips can be had out of a 40" width of fabric.
Then, we're going back to Pythagoreas. I wanted to find out how much length I'd have to cut to get 11 strips that would make my total amount of bias needed. Since bias is always a 45 degree angle, the sides of the triangle (a and b) are equal (trust me on that one too, please), so we can make the equation be:
(c) squared = 2 (a) squared
c is the length that the bias strip will be, and a will be the linear amount I'll need to cut to make it happen.
(That would have been easier if I could figure out how to do superscript in the font)
When you've done the math, and converted the decimals to the imperial measurement you need to use your ruler (unless you've evolved to metric), add at least 1/2 inch for a seam allowance used to stitch the bias strips together.
I've used this formula successfully for several quilts. I don't always remember to round down to the whole number of strips from WOF, and then things don't work so well.
This time, I want to use 2.25" strips. So Pythagoreas tells me it's 12.5 strips per WOF. Plugging in to the formula, 215 divided by 12 = 17.9 I need 12 strips of bias that are 18 inches long. (I forgot to round down to 12 strips, so my bias on this example is only 213 inches. I'm hoping that the fudge factor I built in while measuring the round parts will bail me out on this one. It did on the last one I muffed up)
Now, we do the math thing again, and find that (18)squared = 2 (a) squared, (a) being how much of a strip I need to cut of WOF. Works out to be 12.72, or 12.75 is easier to deal with on a ruler. Don't forget to add half an inch for seam allowance, so we're looking at a 13.25 or 13.5 inch strip WOF.
Here's my WOF strip. Trim off the selvage edges.
Line up your 45 degree line on one side. It hasn't mattered where I make the cut.
Put right sides together, and stitch up the selvage edges, so you have a long strip, with bias on both ends.
Tip picked up from trial and error: If your back of fabric looks identical to the front of fabric, mark with a pencil in the seam allowances on both sides. It will save you some frustration. Since you're probably smarter than I am, you'll do it on both edges of the strip, so you don't have to go back and mark the strips on the other side after you cut them, like I did. ;o)
I'm cutting 2.25 inch strips from the bias end. If my WOF strip is really wide, I'll fold so that the bias edge matches itself and make the cut all in one swipe.
You can use a point trimming template at this time, if you like.
Join them together. If you have remembered to round down, and add in seam allowance, you can arrange the strips so that the two strips that have the joining seam (the selvage edges joined) closest to the ends of the strips are on opposite ends, so that they might be cut off entirely if you're lucky. If you checked your math, that is. And you're lucky.
Joined together, pressed in half, and ready to apply.
In summary, I've found I need:
11 strips per WOF for 2.5 inch bias
12 strips per WOF for 2.25 inch bias
29 strips per WOF for 1 inch bias
Divide total inches of binding needed by # of strips to get the length of the bias (c), and plug into the formula.
Add 1/2 inch for seam allowances.
Live long and prosper.
And now, I have this journaled, so I won't have to do calculations again, and forget to round my decimals!



