I totally agree with this comment. I found that this was my problem with HSTs also. Unless you make a perfectly straight 1/4 inch seam, the results will be off. I can't get it exactly right either, so I have actually started reducing my 1/4 inch seam just a hair, so that the resulting HST are just a bit over what they are supposed to be on purpose. Then using a ruler that has good angle markings, line up the angle lines and trim down to the exact size needed; I get more consistent results doing this.
Originally Posted by
MadQuilter
Dull rotary cutters are no good, that's for sure. I'd suggest you change the blade.
It looks like you didn't square up some of your HSTs and as a result some of them are oversized. In that case, nothing will line up and it is no wonder that you are frustrated. I always sew my HSTs and QSTs oversided and square them up. It may be more prep work but MUCH LESS headache in the long run.