Updated: Jan 7
This month's post is all about sewing precise seams; the second most important element of precision piecing. Almost all quilt patterns rely on a consistent 1/4" seam. Pieces are cut and sized perfectly to accommodate this assumption. But what happens when that assumption is no longer true? Well, things can start to get a little wacky. This is especially true when it comes to more complicated patterns such as those involving smaller pieces, non-90- or 45-degree angles, or where lots of points have to come together. In those cases, taking more or less than the intended 1/4" can really compound until it becomes almost impossible to get your points to match. That's when patterns become nightmares that you wish you had never started and quilting is no longer fun and that's not OK. So here are my best lazy tips for maintaining both consistent and accurate seam allowances.
FYI: This post is part of a monthly series on precise piecing. If you haven't read Part 1, you can check it out here. There's lots of good information for easy ways to cut more accurately, as well as some ground rules. The goal here isn't to make you stress over perfect points (perfect isn't beautiful, it's sterile), but to show some easy habits that you can implement to up your quilting game and ultimately make quilting more fun. Also, if you aren't already subscribed to my newsletter, make sure you sign up at the bottom of this page so you don't miss next month's post!
Accuracy vs. Consistency
I might be splitting hairs here, but there is a difference between accurate seams and consistent seams (accuracy vs. precision, if you’ve ever taken a high school physics class). Accuracy is how close you are to the intended position, the scant ¼”, while consistency is how reliably you maintain the intended measurement, whatever that measurement happens to be. In quilting, this means sewing straight seams. You can be accurate and not consistent, or consistent but not accurate (your seams are straight but closer to 3/8” seam allowance than the intended scant ¼”, for instance). Ideally, we’d like to have both, but most quilters are naturally pretty good at sewing consistent seams. Sewing accurately tends to be a little more elusive. I’m going to be sharing tips to achieve both.
The best way I have found to sew consistent seams is to use a ¼” foot. ¼” presser feet come in a couple of different flavors. Some models have a “flange” or a little plastic piece that makes a wall on the edge of your presser foot which acts as a physical guide. All you have to do is keep the edge of your pieces butted up against that wall and your seam will stay straight and consistent. A word of caution though: it is possible to push your fabric past the flange or not hold it tightly enough to the flange which will lead to inconsistent seams. However, a lot of people find that the physical guide, instead of just the visual guide, does improve their consistency. Make sure to read your manual before using a flanged ¼” foot because most machines require you to set your stitch width to a certain position for it to work.
Non-flange models work largely the same way, they just lack the wall to prevent your fabric from getting too far away from the edge of the foot. On my Janome machine, this flavor of ¼” foot is referred to as the professional presser foot rather than a ¼” foot, so if you’re having trouble finding a non-flanged ¼” foot for your sewing machine, try looking for a “professional” or straight stitch foot instead. The purpose of this type of foot is to visually match the edge of your pieces to the edge of the foot. It takes a little practice, but the visual aid works pretty well.
If you find yourself struggling with consistency, a flanged foot does make things a little easier. Ultimately, I do like a non-fanged foot better though because it doesn’t’ interfere as much when I have to sew over dog ears that are sticking out past the ¼”. More on that later though. I tend to fluctuate between the two depending on the day just because the machine set up is a little longer for my non-flanged foot than my flanged foot for my model of sewing machine (Janome MC6700P). Either can work well though. If what you’re using now is working, just stick with that.
Neither of these ¼” feet guarantees that you are sewing an accurate scant ¼” seam though (no matter what sewing machine or foot model you have). That’s a whole other matter entirely.
Sewing accurately – the scant ¼”
First things first, what the heck is a scant ¼”? Quilt patterns size their pieces to be exactly ½” larger than necessary on all sides to allow for the ¼” of material you are going to lose in the seam allowance. That would all work out perfectly if fabric were completely 2D and had no thickness whatsoever. That’s not reality though. While thin, quilting cotton still has some thickness to it and that thickness means that some of the fabric beyond the seam gets sucked into the seam allowance when the fabric folds over. It's unavoidable. By sewing just slightly less than ¼” seam, you can make up for that little bit of material that gets lost in the folding so that the final size of your quilt pieces end up exactly what they should be. This slightly less than ¼” is referred to as the scant ¼”.
Now you’re probably thinking “how much of a difference does this actually make?” The answer is different depending on what kind of quilt you’re making. It doesn’t make much of a difference if you’re working with large pieces or fairly basic shapes (strips, HSTs, etc.), but if you’re working with small pieces or patterns where 6 or more fabrics are coming together in a point, it can make a huge difference because now all the pieces are either too big or too small to fit together into the puzzle correctly.
You also might be thinking “how much less than a ¼” do I need to sew?” The answer to that question is also it depends. Since you’re losing fabric to folding, how scant you need to sew is controlled by how thick your fabric is and how thick the thread you are using is. Since most quilters exclusively use quilt cotton (which all have relatively the same thickness) and also stick with the same kind of thread for piecing, this removes a lot of the variables. Each quilter should still calibrate themself for the particular way they sew once in a while. The good news is that once you do this, all you have to do is make sure you set up your machine the same way every time you piece. It’s a set it and forget it kind of thing.
You can read all about how to do a scant ¼” calibration here, but the important thing to remember is to sew the calibration exactly how you normally sew. The goal here is to make the machine adjustments to correct for how you actually sew, rather than trying to adjust yourself (provided your seams are generally consistent). That means using whichever foot you normally use for piecing (flanged or non-flanged) and pressing however you normally press (open or to the side).
There are a couple of other things that I find helpful to ensure that I’m sewing both consistently and accurately.
1. Chain Piecing
Firstly, if you haven’t tried chain piecing already, you definitely should! Aside from being very convenient and saving thread, it also ups your precision. Chain piecing is just passing sets of pieces through the machine one after the other without breaking thread in the middle so you end up with a “chain” of pieces. You clip apart the pieces later right before you press them.
How does this contribute to more precise piecing? Well, if you’ve ever experienced the leading edge of your pieces getting shifted or chewed up by your feed dogs, or if you sometimes get big knots at the beginning of a piece, it’s because your thread tails aren’t secure. Since most quilters don’t backstitch at the beginning and end of each piece (why would you when all those stitches will get locked when they intersect the next row), those thread tails can get drawn in and knot or prevent your feed dogs from advancing your fabric as intended. All of this can distort the seam. This problem is made even worse when automatic thread cutters were introduced because the thread tails become even shorter than usual. To prevent this, you can either hang on to your thread tails when you start (like garment sewers do) or secure them in a previously sewn piece by chain piecing. When you start or stop a chain, pass a double layer of scrap fabric (leader/ender) through to secure the thread tails so they’re never loose when you start piecing. (You can see what this looks like in real life in a quick video here.) This simple habit will save a lot of frustration!
2. Your stiletto – a mobile pin
Stilettos are awesome! It’s just a little stick that allows you to hang onto your pieces as they get close to the needle but it can make a huge difference in keeping your pieces from shifting out of alignment as the presser foot applies pressure. If you’ve ever accidentally set the presser foot down on your finger, you’ll know firsthand that they actually apply quite a bit of force! While this isn’t usually an issue when you’re sewing the initial pieces together, when you start sewing over seams, the pressure from the foot can really push things out of whack. Being able to hold those areas together with a stiletto goes a long way in keeping things aligned once the pins (if you use them) are removed. Think of it as a mobile pin. Just be careful not to use the stiletto to stretch the fabric as it goes under the needle. You’re just using it to guide the fabric.
Not all stilettos are created equal though. There are lots of brands and styles, but the main thing to look for is a metal point. This is the one I use (not an affiliate link). Metal is FAR better than plastic because it doesn’t flex anywhere close to as much. It usually also has a sharper point which is much better at gripping the fabric to keep things aligned. Having used both, metal stilettos are a completely different, and way more useful tool.
Alright! That’s the lowdown on the second most important part of precision piecing. Next month we’ll be talking all about pressing and how that affects your precision. Questions? Drop me a line!