How to test for an accurate 1/4″ seam allowance and why it’s important

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It’s always good to test your 1/4″ seam allowance to be sure it’s accurate. If you change machines or maybe you just never tested it, this is a super simple way to be sure your seam allowance is 1/4″. And I have a myth buster or two to share below

MYTH: I have a 1/4″ foot on my machine so I don’t need to test it

MYTH BUSTED: Even if you have a 1/4″ foot for your machine it might need to be adjusted. You can’t assume it is 100% accurate

If you check and it is NOT accurate, then shift your needle one position (which ever direction it needs) and test again. 

On one machine I used a different foot edge with the needle shifted for the most accurate 1/4″ seam on that machine. 

At the END ARE TWO VIDEOs to help you out

Here is my super simple test

• Cut 3 squares 2 1/2″ x 2 1/2″.
• Use 2 different color fabrics so you can tell what you are doing

This is the 1/4″ foot for my Babylock Crescendo.  

I love the guide edge on this one. Your machine may have a different foot, or no 1/4″ foot. 

• Sew the 3 squares in a row.

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• My Babylock’s Crescendo 1/4″ seam foot sews a ‘scant’ 1/4″ seam. Do you see how the seam is to the RIGHT of the line.   When you fold over fabric it takes up a little space, so sewing with a seam just  ‘shy’ of 1/4″ is what works for most people. 
• You need to go through this whole test to see how it ends up .. don’t stop here!
• I have this little 1/2″ wide ruler that i keep by my machine to check things.

• Press the unit so the right sides are up for all 3 squares. Do you see how the seam allowance creates a ridge?
• This is before i pressed it. when you press you need to have it flat. That way as you sew the units together they all are at the correct size.
• now let’s test it!

MYTH: I’m done now I don’t need to test

MYTH BUSTED: no you REALLY DO need to test!

First I measure JUST the center block. It should be 2″ wide. 

Now i measure the entire unit.

It should be 6 1/2″ wide. Why?

• 2.5″ sewn to 2.5″ sewn to 2.5″ = 6.5″ 
• Another way to know what the unit size is will be to add the FINISHED sizes of all 3.. that is 2+2+2 = 6… then add 1/2″  for the seam allowance on both sides (1/4″ + 1/4″) to make the number to nail 6.5″

TIP: To test I like to shift that ruler down and have a straight line across the top and bottom of the patchwork. 

Watch my video on this of mine on shifting the ruler down for measuring that I did for Martingale

So your block is Not accurate 

What to do

• You can shift your needle to the right or left then recheck
• Try a different foot & shift the needle position until it’s where it will give you a consistent accurate 1/4″ seam

ANOTHER THING it might be

It might not BE the foot.

As we sew sometimes we don’t stay true and on the line.

I show you this in the video above. 

MYTH: It won’t matter if my block is the wrong Size, if they are all too small or too large it’s ok if they are the same size.

MYTH BUSTED:  That ONLY works if you have drafted your own setting, or are putting the blocks side by side. If you are using a setting that has sashings, other blocks, units to piece, having incorrect blocks will not create a very sad face for you when you try and sew them together.

It’s worth the time to check your units AS you work 

THINGS to help you:

• My Teach Me books, the one on the left has all my tips for how to get accurate patchwork in a skill building step by step manner
• A  6.5″ Quilting Ruler is pretty much mandatory work tool, get a good one
• BUY the narrow measuring Rulers
• a REALLY Good Iron, 20% off + free Shipping with code PATSLOAN20
• Download this TUTORIAL as a PDF, it’s not pretty and no video..wink!

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