Tuesday, 4 September 2012

TTT - scant 1/4" seams

So far we've gone over cutting and pinning. We need to talk about 1/4" seams. It has taken me a lot of years to master the scant 1/4" seam, so I'm passing on my knowledge to you - and hopefully it doesn't take you as long as it took me.

What is a scant 1/4" seam?

A scant 1/4" seam is very slightly smaller than a full 1/4" seam - about a thread width smaller. In quilting, and any sewing, accuracy is important so that your seams match up, you maintain your points, and your finished product is the size it's supposed to be. If your seams are out even 1/16", then every time you add a seam, you're out another 1/16" - at 4 seams you're out 1/4"; over an entire quilt that can really add up. The reason you need a scant 1/4" seam is that when you press your seams to one side, thread takes up space - it's only a little space - but it can add up.

In the photos below, the seam on the left is a scant 1/4" - green arrow. It's hard to see, but look closely. The seam is just to the inside/right of the 1/2" mark on the ruler (which represents a 1/4" seam from my yellow orientation line. The centre line is my orientation line - yellow arrow. The right seam is just to the right/outside of the 1/4" mark - black arrow - this is a full 1/4" seam ( I think of it as a generous 1/4").

ruler oriented a different way
Test yourself. Sew/draw a registration line on a piece of fabric or paper. Sew a 1/4" seam along that line. Are you scant or full?

A test for scant 1/4" seams

Take two scrap pieces of fabric that are exactly the same width. Mine are 1 3/4" cause that's what's laying around. Sew a 1/4" seam - start with how you usually sew a 1/4" seam. Press open your seam like you would when quilting. Lay your ruler down on your fabric; your width should  be exactly double your original width minus 1/2". In my case, 1 3/4" + 1 3/4" = 3.5" minus 1/2" = 3".
I checked my seam before pressing open. If I line my seam up on my 1/4" mark on the ruler, my fabric falls just short of the edge of the ruler - about a thread width.

a 3" piece - my seams are a scant 1/4"
If your piece is not exactly the right size you need to adjust the width of your 1/4" seam.

How to get a scant 1/4" seam

I have two 1/4" feet. I like the metal one with the black guide the best. It's the one that came with my machine:
my favourite one

I don't use this one too much
If I just use my quarter inch foot and line the fabric up along the black guide, my 1/4" seams are too generous. To compensate, I move my needle position to the right of centre. On my machine it looks like this (I have a Janome 4100). Centre is at 3.5 and I move the needle to 4.3. Make sure your needle will still go through the hole in your needle plate - I need a zig-zag needle plate to do this.
If you can't move the needle, here is another suggestion.
You likely have a 1/4" mark on your needle plate. On my maching it's on the bobbin cover:
the arrow shows the 1/4" mark
If I sew following this mark, my fabric does not go all the way to the edge of the guide on the presser foot but I get a scant 1/4" seam. I feel like I'm not as accurate unless my fabric touches the guide on the machine; this method won't work for me for tiny pieces, such as in my Dear Jane quilt, because the registration mark is far away from the needle.
When I'm sewing a scant 1/4" seam, it looks like this:
I've move my needle to slightly right of centre, my fabric lines up with the guide on my foot, and I'm not on the 1/4" mark on my needle plate BUT I get a scant 1/4" seam.

What do I do now?

Now, you have to practice and play. Every machine is different so try the tests and fiddle around until you get a seam allowance that is a scant 1/4". Try the ruler test and sew two pieces of fabric together. Try a 1/4" foot if you don't have one. Your accuracy will improve and your quilts will look better.