Friday, September 30, 2011

The Mysterious Quarter Inch Seam

Achieving the perfect quarter inch seam has been haunting me since my high school home economics sewing class days.

I've tried many of the tips offered for the perfect quarter inch seam. On my old Singer the presser foot was the width of a quarter inch. I put down a piece of masking tape at the quarter inch mark. On my new Brother I use a quarter inch piecing foot.

But, even though I made sure the quarter inch was accurate, the quilt blocks never really came out the exact size they were supposed to be.

I have finally figured out this mystery....

Are you ready for the mystery to be revealed?

Here it is:

When piecing quilt blocks the size of the seam must be LESS THAN A QUARTER INCH! Its a "Scant quarter inch"! The width of the thread line, the width of the crease made when pressing, and whether or not the pieces are rotary cut or cut from templates, all go into the equation.

When I first got my quarter inch piecing foot, I thought my quilt blocks would magically all be precisely perfect. NOT!!! If I sew my seams butted up to the guide on the quarter inch foot, the blocks will be TOO small. I must sew a couple of hairs away from the guide. When I do this on a consistent basis the blocks come out the right size.

Now, some machines allow you to move the needle position a hair at a time until you get it right where you want it for that perfect quarter inch seam. My Brother machine only allows this for certain stitches, but doesn't do it for a straight seam. At least I haven't figured out how to, if it has that feature.

The bottom line is that you have to measure, measure, measure, and adjust the point that works on your machine, until your block is the right size. Your quarter inch seam may be slightly different than your friend's quarter inch seam. You have to know your own quarter inch seam.

Another point is that some blocks are easier to achieve accuracy with than others.

Sewing this block drove me crazy! The smaller the pieces the harder it is to obtain accuracy. Hardly any of these blocks were exactly the right size and they certainly didn't lay flat. I love the quilt, but just don't look too closely at how the seams match up!

Sewing these blocks is a joy! Almost every block measures 9 1/2 inches and they lay flat.

I've come to the conclusion that every time I start a new block design, I must measure the units of the block and the finished block to figure out where the seam line should be to make that particular block the right size.


Making it vintage said...

Oh my goodness, so much measuring, I can see how you have to be consistent with your seam allowance, I've never been very good with consistency or maybe my machines a little on the old me all that measuring is the
scary side of quilt making, and to me your seams always look perfectly perfect. x

Impera_Magna said...

I read somewhere that back in the early days of the current quiltmaking revival, that ladies marked their fabric with a pencil and then cut the fabric out with a pair of scissors.

Of course, they cut on the outside of the pencil line! Thus, a 1/4" seam was fine.

Today, we cut out with a ruler and a rotary cutter so we need to use that "scant" 1/4" seam to make up for the width of the pencil line.

And yes... the 1/4" seam is hard to master... I know I'm still working on it with each and every block. Much better these day but still not accurate every time....

Denise said...

I agree it will ALWAYS be a challenge to get that perfect 1/4" seam! I love the blocks in the last photo, are they a new quilt you are working on?

Pen Pen said...

Oh girl.... I needed this post. I'm glad I"m not the only one struggling with this! I had not even thought about the difference in rotary cuts and scissor cuts. It makes so much sense. I have tried using a 1/4 inch ruler and marking every seam, but it still doesn't always come out right. Maybe the old template way is best????

Sheila said...

Thank you so much for your insight on the quarter inch seam. I thought I was the only one who struggled with this. Your block are beautiful, can't wait to see the finished quilts. Have a great weekend!