So, we’re ready to sew our pieces together. Why is the 1/4” seam allowance so important? Because quilt pattern pieces include a 1/4” seam in the measurements of the pieces (at least most of them do!) unless otherwise indicated. So, if you do not piece with an accurate 1/4” seam allowance, your 1 1/2 x 2 1/2” flying geese unit, for example, might measure something quite different.
It’s best to test out whether your machine is stitching a 1/4” seam using scrap fabric. Even if your machine comes with a 1/4” foot like mine:
Thickness of thread and needle position (if your machine allows you to move it) can make your seam more or less than 1/4”. So, here’s some steps on how to test your seam allowance:
First, stitch two scrap strips together using the your 1/4” foot as the guide (or if you don’t have one, the marks on the machine throat plate) and then measure the seam.
My seam measures up! But if yours doesn’t, here are some added steps to help to achieve a 1/4” seam. Marking a 1/4” line on your machine’s throat plate is one. Some newer machines already have a mark etched in the throat plate that guides you to a 1/4” seam if you line up the edge of your fabric with it while stitching. Once again, test this on some scrap fabric!
Notice, in the photo above, the etched line on my machine. That’s the marks on the machine throat plate I was talking about. If you want check if that line truly is at a 1/4″, Lay a tape measure across the throat plate and put the needle into the tape measure right at the “0” line. You can see that my 1/4” foot falls right at the 1/4” mark on the tape and my etched line matches up too. Good guides!
If you do not have an etching on your machine’s throat plate, you can mark the 1/4″ with a small piece of painter’s or masking tape at the 1/4 line.
Sometimes, I like to stitch with a scant 1/4” seam (just a hair under) and then trim up the resulting unit to the correct size after pressing, if necessary. This way you are guaranteed that your unit will be the correct size.
I make sure to verify that all the units of a block measure correctly for ease of piecing the block and having it come out the correct size. Remember, a small seam error made on the pieces can magnify if the block has a lot of units. You will save yourself the headache of “unsewing” if you have accurate pieces to begin with! I only takes a little extra time to measure and trim units. It definitely saves you time down the road!
So time to get that quilt pieced!