Accurate Piecing Basics: Quarter-inch Seams
In my last post, we discussed how to use your rotary cutter to cut perfectly accurate fabric pieces, since that’s always the starting point for accurate piecing! Today, we’re going to talk seams. Because all the accurate cutting in the world won’t matter if you’re not sewing with a perfect scant 1/4″ seam.
And yes, that seam needs to be scant. What does “scant” mean? A scant 1/4″ seam is just a thread or two short of exactly 1/4″. And why sew with a scant 1/4″ seam? Because you need to account for the width taken up by the seam itself. Being just a thread-width off may not seem like a big deal at first, but when you add up that thread-width for every seam in your block (or in the entire quilt), it can make a huge difference in the size of your blocks. So remember to keep it scant!
Easier said than done though, right? Let’s talk about how to achieve that perfect scant 1/4″ seam. BERNINA offers a variety of feet and tools that will get you that perfect seam.
Patchwork foot #37/#37D is the most basic 1/4″ foot and is included with many BERNINA machine models. Just line up the outer edge of the foot with the edge of your fabric, and the 1/4″ seam is done for you. The Patchwork foot #37 foot also features markings on the sides of the foot—three markings spaced 1/4″ apart—that help with pivoting around corners (great when sewing on quilt bindings!).
For those of you with 9mm stitch width machines, Patchwork foot #97/#97D is another 1/4″ option, and my personal favorite! This foot is just like the #37, except that the left side of the foot is wider. This allows you to get that 1/4″ seam using the right side of the foot, while the wider left side of the foot is aligned better with the feed dogs on your machine. Fabric will feed through a 9mm stitch-width machine more smoothly and easily using this foot.
The Patchwork foot #97 foot also comes with a movable Patchwork seam guide that screws down onto the bed of your machine, which can be very helpful as well.
There’s also Patchwork foot #57/#57D, which comes with a built-in fabric guide. Some people swear by these fabric guides, while others find the guide unhelpful, because it can be difficult to tell if you’re pushing the fabric up against the guide too much. Either way, you should experiment to see which of these 1/4″ feet works best for you.
Last but not least, don’t forget that you can also use the markings on your stitch plate to get that scant 1/4″ seam. I find that I get my best scant 1/4″ seam by using my Patchwork foot #97D, lining up the fabric just to the right-hand edge of the foot, and also keeping an eye on the 1/4″ seam mark on my stitch plate, which I’ve pointed out in the photo above.
I find that by looking just ahead of the foot, and lining up my fabric with that 1/4″ seam mark (and occasionally checking that it’s lined up with the edge of the foot as well), I can get a perfect scant 1/4″ seam.
Once you’ve got the foot and the method that works best for you, it’s an excellent idea to test your 1/4″ seam, to make sure you’ve got that perfectly perfect scant width. Sometimes, your needle can get slightly out of position and may need to be adjusted in order to achieve a scant 1/4″. Here’s how to test your seam width:
Cut 3 squares, 2-1/2″ x 2-1/2″. (I like to cut two squares from one print and one square from a contrasting print, to make measuring easier later.
Sew the squares together, using your preferred method for achieving a scant 1/4″ seam. Press seams as you normally would. (I generally like to press seams open for the most accurate results—but that may be a discussion for another post!)
Now measure. The square in the middle should be exactly 2″ wide.
And all three squares together should measure exactly 6-1/2.”
If everything measures up precisely, congratulations! You’ve got a perfect scant 1/4″ seam. If you find your squares aren’t measuring exactly as they should be, your needle position may need to be adjusted. This can be corrected by your BERNINA Dealer, or you can manually adjust the needle position on your machine. (Though if you’re using a single-hole stitch plate, you will want to be cautious about manually changing the needle position.) If your sewn pieces are measuring too large, your needle should be moved to the left. If your sewn pieces are measuring too small, your needle should be moved to the right.
I hope my “Accurate Piecing Basics” series has been helpful, and is allowing you to piece more accurately already! Happy sewing!