I am not an expert, there are others on this board that will have the best answer for you. As I see it you may have 2 problems going on. 1. remeasure you squares and triangles. They appear to be different. Accurate as possible cuts are very important. 2. Consistent 1/4" seams are important. I do what is called a scant 1/4" seam. One or 2 threads short of 1/4 inch seams.

Hope this helps a little:) Welcome to the board.

There's a few Tuturials on this board for that. You can try looking in the search...or here is one that may help you


http://www.quiltingboard.com/t-8342-1.htm

How are you making your HST's? I find it easiest to cut two squares 1 inch larger than the finished size I want. Draw a diagonal line on on square. Sew 1/4 inch on each side of the line, cut apart and square up.

Here is a link that explains it well. The instructions say 7/8 inch larger but I do 1 inch. I refuse to measure 1/8!

http://quilting.about.com/od/quickpi...squaretria.htm

I probably don't know what I'm talking about, but it looks like maybe you needed to start with larger half sq. triangles. Did you use the same size sq. (and cut on the diangle) to make you hst? If so, that may be the problem. The sq. would need to be larger to account for the seam allowence. I can't remember the formula, but someone on here will. Your block will be lovely when finished.

that is one of those things you learn along the way. I usually cut about 1/8" bigger, but have even gone 1/4". It is easier to "square up" then like this find out that they are too small.

"Square up" is to make the squares all the same size by trimming to a certain required measurement after you sewn the together like the half-square triangles.

So basically for a 2.5" inch square I need to cut the square 3 3/8' and then cut it diagonally, right?

Welcome from chilly Atlanta. Glad you're here.
You must add 7/8 inch to each side of the HSTs before joining them together.

At this point, I would probably cut down the squares to fit the HSTs. The block will be smaller, of course.

You are right on, most will tell 7/8" larger, but why not 1" and make life easier when rotary cutting. Yes, you will trim alittle, but you will have perfect size half square triangles.

I believe that if your squares are 2", the squares you cut to make the triangles have to be 2 7/8". If memory serves, you add 7/8" to the size of the square you are wanting to end up with after making the HST. Connecting Threads has a little tutorial on it: http://www.connectingthreads.com/tut..._HSTs__D4.html