I'm no expert but that seems to be fine with me, and I had to learn the hard way too, and I make mine a little big too but some designs that doesn't work either when you go to cut them down so I have found out. Live and learn, but would 1/8 of an inch matter? since we are going to put strips of fabric between the blocks? or those could be outside blocks, you more experienced quilters chime in here because I really don't know
OK, so in this situation, I have a couple of things to say:
1) For
me, if I was making blocks for my own quilt, I would like 1/8" or less of difference. BUT, you're right, we'll be putting fabric strips (or alternating blocks, or alternating squares, or something) in between them. I've had some of my blocks come up 1/8" or so short from one block to another. If your scant 1/4" seam is just the littlest bit off, you're going to see a greater difference if you have a lot of seams - that's a lot of places for that seam to be off. You can try using a 1/4-inch foot, if there's one available for your machine (mine has a little edge as a fabric "stop", like
this one). If you don't have a machine with fancy electronics, you can use a fridge magnet (or two) and make your own fabric "stop", or build up a 1/4" fabric stop with masking tape or similar. Sometimes you can set your needle to one side or another, depending on the foot you have, and that will allow you to achieve an accurate 1/4" against the edge of the foot itself.
2) If you do more than one or two swaps, you'll see that this can happen. You learn to accommodate the differences. Everyone is different, every machine is different, sizes can even be a tad bit off between one ruler and another! Measuring mistakes and cutting mistakes can occur as well. We're all human. I always try to use the same
kind of ruler; almost all of mine are now Creative Grid although I do still have a few other brands, and I try to use the same brand across the project. It's not always possible to use the same ruler. The 24" long ruler I use to cut long strips is just not practical for 4" squares.
You can even come up with slightly different measurements due to the way you iron, or which side of the fabric you have cut or stitched, relative to the selvedge edge.
I'm cutting mine as 4" squares, sewing the half-square triangles from those, and cutting them down to 3-1/2" before sewing the block together. Doesn't mean mine will be perfect. I still haven't figured out which way all the triangles are going to be ironed to make everything fit together the easiest. Normally I iron seams toward the darker fabric, but that doesn't always end up being the easiest way to sew things together. I'll "nest" the seams when I can.
