How to Sew a Curved Edge to a Straight Edge

Joining unlike edges can be quite a daunting task, but with the right methods, you come to realize it isn’t all that difficult.

Getting to achieve smooth and neat curves takes patience and skill. Joining your curved edge to a straight edge with accuracy will result in an attractive and elegant curve.

Regardless of the materials that you are using, the methods remain the same. Therefore, if you are making rounded bags, backpack bottoms, collars, hats, or pockets, you can comfortably follow through the processes outlined below.

How to Sew a Curved Edge to a Straight Edge?

Are you questioning where you’ll begin? Well, here is where! Have your pieces ready. This article will take you through sewing seams using a straight edge and a curved edge.

It may seem challenging, which it is, but there are ways to hack it, and we’ll show you just how. Remember, practice makes perfect!

Tools You’ll Need for a Perfect Curve

You’ll need some helpers along the way to achieve an excellent curved seam. These include:

1. Sewing Machine

Your everyday, standard sewing machine will work just fine. However, this depends on the fabric you are using—thick materials like the ones used for making bags require heavy-duty sewing machines.

2. Scissors

When working with curves, you’ll either need to clip or notch the seam to achieve a flat smooth seam. Use a sharp pair of sewing scissors.

3. Thread

Get the appropriate type and color of thread that goes with your fabric.

4. Fabric Marker

You will use a fabric marker to draw on your fabric before beginning to sew. It will act as your guide.

5. Ruler

With curved seams, you’ll need to have your measurements right and accurate. Use a ruler to estimate your material and intervals between markings.

Steps to Sewing a Curved Edge to a Straight Edge

Now that you are equipped with all the tools you need, let us get down to business.

Step 1: Take your fabric with the straight edge and place it side up.

Step 2: Fold the fabric in half. It will help determine the midpoint. Then, mark it with a fabric marker.

Step 3: Now, you can repeat the above two steps with your rounded piece. Fold it twice to make four marks on the left, right, top and bottom.

Step 4: Take your ruler and make marks on the edge of the rounded piece making sure they are at an equal interval. It ensures that the marks match regardless of where you begin sewing.

Step 5: Take your straight piece and place it side up. Place your marked rounded piece on top of the straight piece side down, making sure you match the center marks.

Step 6: Now, hold the rounded piece and walk it 3/8″ at a time.

Step 7: Using your fabric marker, make marks on both the rounded and straight fabric. You can do it until you reach the seam allowance.

Step 8: You don’t have to worry about the size of the seam allowance; your pattern will tell you just how much it is. If you are sewing curves within a circle, you may want to make closer marks.

It is to prevent loosening the circle seam, which usually bears terrible effects. You can see that on cheap bags.

Step 9: To make your curve smoother and make your seam allowance lay flat, you could clip the seam allowance by making notches at regular intervals or reduce it by cutting a piece off.

Using pins may not work well for this procedure. You’ll discover that it is much more comfortable and better sewing without them!

Tips for Achieving a Smooth Neat Joint

Some items need to be curvy!  You don’t want your curve coming out wrong. Here’s what you can perform to make sure you always have smooth neat curves.

1. Mark Before You Sew

It can be quite tricky to maintain an even seam allowance as you sew with your machine while following the fabric curve. To ease this process, you could measure the seam allowance then mark it on the fabric with a fabric marker.

It will significantly help you concentrate on the fabric getting to the machine needle rather than the seam guide.

2. Look Ahead

A curve is a collection of small straight lines, in this case, stitches. If you focus on a small number of stitches at any particular time, you will sew more accurately.

Making for a curve may make you drag material from beneath the presser foot. Even more, you may turn the fabric too soon. Consequently, you end up with uneven seams and twisted stitches.

Firstly, stick your sights to the machine needle. With this, high and extensive curves may appear less challenging. Gently push the pieces to the side with your fingertips to guide them around the curve.

3. Shorten the Stitch Length

When making a tight curve, it gets easier if you use a shorter stitch length than a longer stitch length because the machine will move the fabric more slowly under the presser foot.

Another great advantage that this choice comes with is that the curve looks less angular.

4. Walk, Sink, and Pivot

Sometimes, your machine will be able to make a sharp turn to stay on course around a curve, especially a sharp one, but sometimes it won’t.

The handwheel does an essential job of walking the needle through each stitch, so when you use it, it gives you more control over where the stitches go and help you keep them even.

Hold your hand wheel, sink the needle into the joint fabric, slightly lift the presser foot and pivot your fabric slightly before letting down the presser foot.

Do this every time you see bunched-up fabric around the presser foot.  The fabric relaxes and lets you go on sewing smoothly.

5. Scale Down your Seam Allowances

With a large seam allowance, more fabric needs to go into the curve, resulting in wrinkles. When working with a pattern that has ?” or a larger seam allowance, you may want to reduce it to ?” to make it easier for you to pin and sew.

There are fewer chances to make mistakes if you reduce the seam allowance before cutting the fabric. Reduce it on the pattern pieces.

However, if you have already cut your pieces, it is okay to reduce them before sewing them together.

6. Match the Centers

Since you are using a straight piece and a curved piece, match the two pieces’ centerlines. You could mark them with a fabric marker to make it easy to match them.

When you pin your two fabrics together, match one end of the seam as well. Doing this helps to distribute the fabric evenly when you sew them together.

7. Cut Notches or Slits

Convex curves will have more fabric in the seam allowance than the actual seam line. Leaving them as they are, makes the joint bulky when turned right side out. Besides, it doesn’t look pleasant.

Reduce the bulk by trimming the seam allowance then snipping small notches within the left seam allowance. Take care not to get to your stitches!

It reduces the amount of fabric getting shoved against the seam’s edge and leaves your project looking pretty.

On the other hand, concave curves have less fabric in the seam allowance than at the actual seam line.  Cut small slits into the seam allowance giving room for stretching, then flatten it out when turning the project right side out.

8. Smooth Out Curves

When you perform the sewing process, turn the project right side out and push out the curved seam with a pointed object. Avoid sharp objects as they may poke through the seam line.

An iron box will come in handy to help get out the last bumps and wrinkles. The weight and steam from the iron result in a more professional finish. You can also use a tailor’s ham.

What Do You Do With a Curved Seam to Make It Smooth and Flat?

No one wants a bulky seam. It is ugly, to say the least, so we can guess it’s fair to say that it is compulsory to reduce the seam allowance before turning your project right side out.

Making small slits on what is left of the seam allowance also helps to reduce the bump.

What Is the Difference Between Clipping and Notching?

Clipping comes in handy when attaching a curved edge to a straight edge. It allows your fabric to stretch out. Notching, on the other hand, is mostly done on convex curves.

It enables the fabric to come closer together without bunching up by getting rid of the excess fabric.



I'm Jessica Flores, a professional fashion designer and an expert seamstress. Crafting has always been a deep-seated passion of mine, one that has flourished and evolved over the years. I've dedicated considerable time to both studying and practicing in the realm of fashion and sewing, amassing a wealth of experience and skills. It brings me great joy to share these insights and experiences with you all, hoping to inspire and foster a similar passion for the art of sewing.

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