Here's a tutorial for any quilter...but specifically for those taking my Farmer's Wife Quilt Revival Classes.
Before trimming a Half Square Triangle, line up the diagonal line of the ruler with the diagonal seam of the hst. The outer left hand side line and bottom line of the ruler should be directly ON TOP of the fabric.
This will help with accuracy for the desired half square triangle size. In this case 1-1/2".After sewing the hst to a loose triangle, i 'heat set' my seams first before pressing them to one side. This is an important step. It allows one to line up the edges of the two pieces to ensure they are both square and straight. Then carefully press the seam to one side without distorting the unit.
When sewing units together that have 'points', make sure the seam is pressed to the side that allows the intersection to show. Stitch directly through the intersection. You can see below my needle is just about to stitch through the intersection. In doing so, am confident i have not cut off my 'point'.
Another helpful tip when stitching pieces together. You may have 'tails' that stick out beyond the seam allowance. My needle below is almost to the loose triangle 'tail' that is underneath my presser foot.
Maintaining a 1/4" seam allowance, my needle should stitch exactly where the 'tail' ends.
I don't recommend pressing all the seams open. Sometimes seams are easier pressed to one side allowing them to 'nestle' up against each other making it easier for seams to line up. However, in the picture below where lots of seams intersect and create bulk, it is perfectly fine to open up that last seam to distribute the bulk.One more tip on squaring up a unit. None of us are perfect...i certainly am not as you can tell by the picture below.
This unit should measure 3-1/2". I place the diagonal line of the ruler on top of the diagonal seam line. I also line up the opposite diagonal line through the half square triangle units. Now i trim the right side and the top of the unit. Flip the unit around, line up the ruler again and trim the other side. Watch out not to trim more than a quarter inch next to the half square triangles. That is your seam allowance. Take a look at the top left hst. See the white tip of the triangle? The 1/4" ruler line is just below the tip. I'm going to avoid trimming that area because when i stitch it into another unit, i don't want to cut off that point.
That's where pressing can help. Before i trim this block, i might go back and repress to see if i can square up this block a bit more before i take the cutter to it. Be careful not to distort the block too much with excessive pressing which can create waviness.
I hope this has been helpful. When working with small 6-1/2" blocks as in the Farmer's Wife Sampler Quilt....Pressing, Trimming and a bit of 'Fudging' go along way.
To learn more about my Farmer's Wife Quilt Revival Classes, click HERE