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Grading Seam Allowances: How and Why

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Seam grading is like stair-stepping. Don't worry, it's not the aerobic kind from the gym. It's the process of turning a standard seam allowance into layered tiers of fabric. The result is less bulk, which means a smoother finish from the right side. It's another one those very basic techniques that can make all the difference in the professional look of your project. It is done by hand, so it can be a bit time consuming based on the length of the seam being trimmed, but it makes a tremendous difference. Bulky, lumpy seams are not very pretty. Crisp, flat seams are best!

Not every seam requires grading, but it can be done on any seam. It is more necessary when working with a) thicker fabrics, b) seams that will be pressed together and to one side rather than flat, or C) seams that will be sandwiched between other layers, such as on a waistband or along the top of a bag.

Some people are reluctant to grade because they feel it will weaken the seam. But really, unless your project is something that is going to be laundered day-in-and-day-out, the strength of the graded seam will be fine. Plus, graded seams can still be finished – even if it's just with a seam sealant rather than a machine finish. And, the results are worth it! 

Our thanks to Janome America Education Coordinator, Nancy Fiedler for providing these helpful tips, techniques, and samples. She used bright colors against white in her samples to best show the different widths of the layers. 

To help keep your grading precise, we recommend two types of scissors: 

3"- 5" sharp, pointed scissors, sharp enough to cut all the way down to the point.

Duckbill Scissors; sometimes called Appliqué Scissors. 

Grading a faced seam for a smoother appearance

  1. To start, at any seam intersections, trim the ends of the intersecting seam allowance at a diagonal.
  2. For the smoothest look, it's best to start trimming on the inner side of the allowance (the facing side), leaving the widest allowance on the side of the seam that will lay against the right side of your project. 
  3. Duckbill scissors make trimming easier as they prevent you from accidentally snipping the layer beneath.
  4. Trim the first layer about ⅛" from the seam line. 
  5. Trim second layer about ⅛" beyond this first layer.
  6. If your seam has more than two layers, simply graduate each layer accordingly. For example: trim layer one to ⅛", layer two to ¼", and layer three to ½".  

Grading a curved seam

  1. If the seam to be graded is curved, clip the curves first.
  2. Use small, sharp scissors that can cut all the way down to their point, allowing you to snip to within just a few threads from the seam.  
  3. For an outside or convex curve, first make "V" clips to give the seam the ability to ease - or slightly stretch. 
  4. When these clips are done, grade the layers of the seam allowance as above.
  5. For an inside or concave curve, simply take a single clip about every ½" for easing, then trim the layers of the seam allowance. 
  6. For more tricks about sewing and trimming curves, see our full tutorial: Sewing Smooth Curves Every Time

Corners

  1. To make a sharp corner, first grade the seam allowances in either direction from the corner. Then, clip the corner at a 45° angle, cutting close to but not through the seam. 
  2. For more about stitching and cutting corners correctly, see our full tutorial.

Pressing

  1. Once the grading is complete, and with the project still wrong side out, press the graded seam allowance to set it. 
  2. Then, press the seam allowance together and to one side. If working with a facing, you always press the seam allowance toward the facing. 
  3. If you are still worried about bulk or about the seam rolling, you can understitch the seam in place against the facing side. We have a full tutorial on understitching if you are new to this technique. 
  4. Finally, fold the seam right side out into its final position and press well from both sides. 

Our thanks again to Janome America Education Coordinator, Nancy Fiedler for her help with this tutorial. To stay up-to-date on all the news from Janome, visit their website and/or follow the creativity on their blog, Pinterest, Instagram, Facebook, Twitter, or YouTube.

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Comments (7)

Laura Palulis said:
Laura Palulis's picture

Finally, I understand exactly what grading a seam allowance means! Thank you!

Liz Johnson.Editor.Sew4Home said:
Liz Johnson.Editor.Sew4Home's picture

@Laura - You are so welcome. It's excellent to know you understand the technique!

Mehri Jayne said:
Mehri Jayne's picture

This is a read every new sewer should read.  When I started sewing 40 years ago, patterns would tell you to grade certain seams, now patterns just say trim.  

Liz Johnson.Editor.Sew4Home said:
Liz Johnson.Editor.Sew4Home's picture

@Mehri Jayne - Thanks - and we agree. It's one of those very important basics.

BarbaraL said:
BarbaraL's picture

Terrific tut - thank you so much.

Where might one find the pattern for this stunning bag design ?

BarbaraL said:
BarbaraL's picture

You are an angel. Thank you for the reply. I truly appreciate this !

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