I use a product called Stitching Lines (www.marinaandcolusa.com). I find them very helpful keeping the stitching lines straight. I also find that the practice of making my squares slightly larger (1/2 inch or so), sewing and then trimming down to 4 1/2" for instance works best for me (some people call it "squaring up"). I always wash my fabric and use spray sizing or starch before I ever cut it. I like to use it after I've cut my square down as well. I am making HST's for an Edyta Sitar quilt and seem to be having good luck with this method.

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I am making 3,000 2" hst and I am using several techniques. A new one I used, was take a 5" square, iron on the diagonal a nice straight line, sew 1/4" on each side of your ironed line, do on both diagonal lines. Sew both lines. Go back to iron. Now iron in quarters. Cut on the iron lines and the sewn lines diagonally. You end up with 8 2" hst.
You also might like the printed hst. I use triangulations, but there are free programs out there. You simply print out the size you need - I use doodle pads cut down to printer size. Sew on the lines - actually I sew a hair inside of the lines. And voila, perfect hst. There are also rulers for this job. Find one that works for you.
HTH

I have been making a quilt with oodles of HSTs of all different sizes and I found Triangulations to be a life saver. It comes with a CD that enables you to print HSTs and QSTs in increments of 1/16". Basically you place your two fabrics right sides together, print the appropriate size triangles from the CD and lay that on top and pin. The printed paper has cut and sew (continuous line, by the way) lines. Start sewing. When done you just cut them apart. Depending on the size needed you can have anywhere from 4-32 + on a sheet. I have even used it for cutting single triangles of weird sizes (lets say 2 7/16"). I print the triangle sheet on my printer, spray with temporary adhesive and lay it on the wrong side of my fabric and cut on the cutting lines. The fabric doesn't shift and you have perfect triangles. The quilt pattern I was using used templates (ugh) but by measuring the sides of the template, I was able to use Triangulations instead. I also found out that pressing your seams OPEN helped me achieve greater accuracy. On matching triangle points I have resorted to using Elmers SCHOOL glue instead of a pin to match perfect seams. Works like a charm. After sewing I pop open the seam and iron flat. Good luck and hope this suggestion helps.

this indeed is a quick way of making hst, but I think for a more advanced piecer because when you do them this way you are dealing with bias edges when joining them....But the "old fashioned" way of sewing the diagonal-either one on each side of line or one on each side of line...depending on the size of those squares as opposed to what size you want those hst........easier and "safer" for joining.....straight edged hst

I have one of these! I keep forgetting about it when I make my HST; duh!!! I remember that it cost less than $4 at my LQS. I'm gonna have to put it someplace that I will see it!

Make sure you read the instructions on how to do this as you have to cut the squares larger than your completed HST's.

Look on youtube for a tutorial from Missouri Quilt Company. Jenny did one last week and I can hardly wait to try it. froggyintexas

I also cut the squares a little larger. After they are sewn together, cut apart and pressed, then I use one of the square rulers and trim to size. It does take a little more time but I get good squares and points.

I just made a sailboat quilt top with pinwheels (lots of HSTs). I decided to do the math and cut my squares the correct size, since my machine is pretty good about straight lines and has a helpful 1/4" seam line guide (I use a clear foot). I prefer not to mark the fabric, so I cut the squares in half first, then sew a 1/4" seam on the two triangles right sides together.

To make your HST squares come out to the right size as your whole squares, you need to add 1/(2*sqrt(2))" to the sides, or 0.354" (slightly less than 3/8"). You have to add less than the 2 x 1/4" (1/2") seam allowance because in the square dimensions your seam is actually applying on a diagonal, and the horizontal distance eaten up by the diagonal is less. So for me, I wanted 3" squares. That meant cutting 3.35" squares (I cut at 3 3/8"). Technically, they end up being 3.021" square, but that's within my sewing margin of error I think. I could have squared them up to 3" exactly, but the difference was so small it didn't really matter to me (it's only a crib-sized quilt), as I just squared up the terminating edges of the quilt once everything was pieced and that worked fine with my pattern. If you have a large quilt, or all your blocks are HST, then you're better off squaring them up to exactly the size you want or it'll be really noticeable once you start to match seams at opposite ends. For instance, joining two blocks together puts you off by 0.042", but 10 blocks puts you off 0.21" (nearly a quarter of an inch), 50 puts you off by 1.05", and 100 puts you off by 2.1"!

When I am making a lot of HST this is my favorite method. Very easy to make them acurate.