A plain seam is the stitching made to join two fabric pieces together, leaving some seam allowance, usually 1/2 inch or 5/8 inch. You can sew this by hand ( using back stitches or any easy hand stitches) or using the sewing machine with a straight stitch ( or tight zig zag stitch). This is the seam made for most of the fabrics, in all kinds of sewing, be it making clothes or home furnishings or accessories.
How to sew a Plain Seam.
Step 1: Prepare fabric for the plain seam.
Mark the seam line with chalk or any other marking tool; finish the seam edges with a serged finish or zig zag stitches to prevent fraying. Keep the fabric pieces for the seam, right sides together, aligning the seam markings of the two pieces.
Step 2: Make Tacking stitches or pin in place.
Pin if you want to, so that the seam line would not shift. For some delicate slippery fabrics or hard to manage fabrics or many layers of fabric you may want to make tacking stitches. Tacking stitches are simple hand sewn running stitches made with a thread and needle, made so that the fabric pieces are temporarily joined together
Learn more about tacking stitches here.
Step 3: Position correctly.
Before you start the seam stitching, keep the fabric on the needle plate under the needle aligning the seam allowance against the seam guide which is there on the needle plate of most machines. If you have cut the fabric properly, just by guiding the fabric keeping this seam guide aligned, you will get a straight stitch.
Use your hand to move the balance wheel so that the needle is inserted into the fabric.
When you are sure that needle is in the right place, lower the presser foot. Take the thread of the needle and bobbin to the back and hold it there with your left hand.
Step 4 : Make Anchor stitches.
When you start stitching you may want to secure the stitch /anchor the stitch by making one or two back stitches, or stitch in the same place with stitch length kept at 0. This is necessary so that the stitching would not unravel after sometime. It is similar to the thread knots you make in hand sewing.
Step 5: Start the plain seam stitching.
Continue sewing along the seam marking. You may be using the straight stitch ( Mine will usually be with the 2 point in the stitch length lever) for almost all kinds of fabric. But if it has any stretch ( all stretchy fabrics like knits) you will be better off using a narrow tight zig zag stitch – this stitch will stretch along with your fabric,and the seam line would not break.
Step 6 : Finish with anchor stitches.
After the stitching is done make back stitches to anchor the stitch.
If you want further reinforcing the seam – You can make a second stitch over this one. This is especially done for fabrics with weak weaves, or which looks like it will fray. Some people make a parallel row of stitching along the stitching line.
You can remove the tacking stitches now, if you have made them
Step 7 : Reduce the seam bulk.
Clipping and trimming the seam allowance is needed to reduce the bulk created by seam allowance. This is especially needed when you have to turn the seam allowance, to the inside or for a curved seam. For eg : for Facings.
You can either cut the seam allowance in different widths – this also reduces the bulk. This is called grading the seam allowance.
You can make small snips all along the seam allowance (as in the picture above) – for shallow curves this is fine.
For deep curves like a circle you will have to make V shaped notches to reduce bulk
For some spaces you may have to cut the layers as well as make snips on the seam allowance.
Step 8 : Press the seam and seam allowance.
The pressing is optional but it is important for a nice looking seam line. You get smooth seams when you press. Most of the professionals press the seam allowance as they sew. They have a pressing area specifically near their sewing machine for this – which more than explains the importance of this step.
First simply press the seam line on the outside and then open the seam allowance and press it open
This pressed seam allowance make the fabric look like a butterfly which is why this seam is called a single needle butterfly stitch.
When you have to join two fabric pieces which consists of two fabric pieces joined with a seam, the pressing you have done is going to reduce bulk and help to align them perfectly
How to stitch a plain seam at corners
When you are stitching a square seam you need a sharp point at the corner.
To get this sharp point, you have to stitch so that when you reach the corner you leave the needle in the fabric and raise the pressure foot.
Now without taking the needle up, pivot the fabric so that the other side seam is facing you. Now lower the pressure foot. continue stitching. This way you get that sharp point.
How to stitch a reverse corner
This kind of reverse corner is seen when sewing hem facings, V-neck facings, sleeve hems with slits etc. Here the seam allowance comes to the inside.
You will need to stitch the seam as described above. And then clip the seam allowance in the corner, very close to the stitch ( do not clip too close that you cut the stitching). This clipping is needed so that the seam can be turned smoothly.
How to sew curved plain seams
The most important thing to remember when sewing curved seams is to clip the seam allowance. You may have to cut away v shaped notches on the seam allowance
For most fabrics a plain seam with a neatened fabric edge finish is enough. But some fabrics like heavy weight fabrics, or sheer fabrics call for other types of seams for them to look nicely finished. You can check out these other seams in this post : 17 different types of seams.