I’ve had a lot of emails recently about cutting fabric straight. I have written about safety with rotary cutters before in the beginner quilting section, but here I’m going to concentrate on the steps that you can take to make sure both that the lines that you cut are straight and that the fabric is straight before you begin to cut. I’m going to go right back to basics, so forgive me if I repeat things that you already know.
First point is the fabric itself – it’s made of threads running along the length of the fabric known as the warp. This is also known as the grain of the fabric – on a paper pattern you will usually see an arrow showing you how to position the pattern piece relative to the grain of the fabric. The threads running from side to side and weaving over and under the warp threads are known as the weft. These run from selvage to selvage. When you cut fabric straight, your cut will run in line with either the warp or the weft and this is the ideal. If you are cutting a triangle, one of your cuts will be diagonal (known as ‘on the bias’) and this side of the triangle will be less stable than the other two sides which run along the line of threads. This diagonal side is more likely to stretch, which is why you need to handle triangles carefully.
So, how do you make sure that the fabric is straight when it’s laid out on your cutting mat? Lay the fabric on your cutting mat. Generally fabric comes from the shop folded so that the selvages are together and there is a fold along the length of fabric. Line the fold up with one of the lines on your cutting mat. The other end of the fabric will be off the bottom of the cutting mat so fold the selvages up so that they are nearly in line with the fold. The fabric is now in four layers and it is completely on the cutting mat. Adjust the top layers so that the fabric lies completely flat. This is more important than having the edges of the fabric in line with each other.
Line your ruler up close to the right hand edge of the fabric, checking that the ruler is lined up with the same marking on both the top and the bottom of the mat. The four layers of the fabric are probably not in line with each other so make one cut to trim the uneven layers. Remember to cut away from yourself. Usually this will give you a straight edge and you can now continue cutting the strips that you need for your quilt. Sometimes, however, you will find that a strip of fabric has a bulge in the width rather than an even width along the entire strip. I think that this is the element of cutting fabric straight that worries quite a few people.
Pick the entire piece of fabric up and hold it with the two selvage ends in your left hand and the middle of the fabric in your right hand. Line up the ends in your left hand with each other and look towards the bottom of the fabric: are the two ends still in line with each other? If they are not, move one of the selvage ends in your left hand either up or down and you will see that the edges at the bottom of the fabric move either further away from each other or more in line with each other. Continue adjusting the edges until they are in line with each other all the way down the length of the fabric.
Carefully place the fabric back on the cutting mat with the selvages now in line with each other. What you have done is straightened up the fabric so that your cut will follow along the threads of the fabric. This is one occasion when I think that the video may well explain what I mean more clearly than words can: