Scant 1/4 " seam
 

Can someone explain this to me? Why can't the designers just work an exact 1/4 " seam into the pattern?

Linda

The fact is that when the fabric is folded, as it is at every seam, something is lost in the seam itself. It would be impossible to design patterns that made up for those few threads. You would have directions that told you to cut 2.52 inches for one piece, and 1.77 inches for another, and you would never be able to measure that accurately. It's a lot easier to just learn to sew a scant 1/4".

Is that true on all quilts or just certain ones?

You can sew the seam at an exact 1/4" and use your dimensions. Of course, you may lose some points in the process.

I just got done refolding and fondling a bunch of fabric in my stash. 90% is LQS with some Joanne's and Walmart thrown in for good measure. Some of the fabric is a bit thicker than others and some a bit thinner. As Dunster said, the fold takes up some space -- and the thicker fabric takes up a bit more. What is important is the finished size of your block. You need to make the blocks in a quilt a consistent size so that you can assemble them and not throw the pattern off (like Madquilter said -- you may lose some points). It is best if you do a test to see what you have to do to get a consistently sized block.

To do this, I cut practice pieces from the fabrics that I am going to use -- 2.5" x4.5' works. Stitch them and measure them. The block should measure 4.5"x 4.5"". If it doesn't, then make adjustments in your needle position or in the edge you run your fabric against. I use a lined note card -- the lines are 1/4" apart -- to get a good visual and I mark the information about where the needle should be positioned so if I go back a week later I can remember what I found and don't have to start over again with the measurements.

Not only does the fabric thickness make a difference but so does the thread. My seams got a lot more accurate when I changed to Aurifil for piecing.

I've yet to be shown here. Scant quarter inch seam vs quarter inch seam makes that much of a difference as long as you are consistent. Plus I do my own measuring for borders and not rely on pattern measurements.

Aw, Aurifil, my choice too! Love it! And it makes piecing easier for me too!

Same here. I've used alot of Quilters Cache patterns which most, if not all, call for a scant. I use a full 1/4 and have never had a problem.

If you are required to sew two or more seams to make a section that then needs to be sewn to a block that is cut to for example, 4.5", then you need for the pieced block to finish at 4.5". Depending on fabric and thread and how many seams you are sewing, it can make a difference if you don't use a scant 1/4".

If all the blocks are pieced, then a consistent seam will work, but as MadQuilter said you may lose a point or two.