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Why is my 1/4″ seam allowance never quite right?

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Question from a reader:

“I always try to be very careful about my 1/4” seam allowances, but my blocks always seem to end up smaller than they are supposed to be.

For example, I just made four Maple Leaf blocks for a table runner made up of pieces 2 1/2″ square and 2 1/2″ half square triangles. The finished block should be 10 1/2″, but mine are all 10 1/4″.

Where am I going wrong?”

You are very wise to be concerned about your 1/4″ seam allowances. And by using that term, right away you can get in trouble.

If you use exact 1/4″ seams, you will find that your blocks will be a little small. The reason for this is that some fabric is lost in the turn of the cloth when you press the block. We need to learn to sew and use scant 1/4″ seam allowances.

To do this you will need to place a marker on the throat plate of your machine. Don’t rely on a special 1/4″ sewing machine foot. Always determine that scant 1/4″ mark for yourself.

Cut a strip of four-squares-to-the-inch graph paper. Trim it along one of the lines. Place the graph paper under your presser foot and pierce the paper just shy (by a couple of threads of fabric) of the first line. Place a piece of masking tape or adhesive-backed moleskin right along the edge of the graph paper. That will give you a scant 1/4″ seam allowance.

After beginning a project, always use the same machine, and sit in the same chair while you do your piecing. It is amazing, but you can get a different measurement when you look at your work from a different angle.

Repeating the same routine will give you the same perspective each time and help your mind memorize the steps and even muscle movements while you work. You’d be amazed how comfortable you will get if you work in the same environment for all of your projects. However, keep in mind that you have to have a safe environment to work in. That is, working at the proper height and technique so as to prevent injury like carpel tunnel syndrome.

If you do think you have repetitive strain injury, I’ve found these gloves very useful in reducing pain.

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