HST Block Size Cutting Question

dan_the_mailmanJuly 9, 2011

I've been doing squares and rectangles for a long time, but I've always been a bit nervous about triangles. I'd like to make some HST blocks which will be 12" and 6" when finished. My method will be to cut out solid blocks, then use my rotary cutter and a ruler to cut them on the diagonal before sewing the various colors together to make the finished blocks.

Here's my questions for all of you pros out there.

1) What size should my beginning block be for the 12" block before cutting it?

2) What size should it be for the 6" block?

I've read about a lot of different techniques in my quilting magazines, and the simplest seems to be cutting solid-colored blocks in half with my rotary cutter, and mixing the triangles.

Can someone help me do this right, and not waste fabric?


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It's hard to sew accurate HST blocks when you cut triangles first. When you do this and then sew along that diagonal edge you are working with the bias. This is the stretchiest direction of the fabric, thus it often creates a block that is not accurate.

There are a few different things you can do about this...
1) Starch the daylights out of your squares before cutting them into triangles. The stiffer they are, the less they stretch. Then sew them together. [Not usually a favored approach due to all the starch]

2) Take that same square and DRAW a line on the diagonal with a fabric pen or sharp pencil. Layer this with another square and pin well (away from the drawn line). Sew 1/4" away from both sides of drawn line. [You can also draw lines 1/4" on either side of the diagonal if you don't have a foot or machine setting that does 1/4"] After sewing, cut along the diagonal and you end up with 2 HSTs. [One draw back to this method might be that you end up with 2 HSTs that are the same, but usually you can place them away from each other in a quilt/block so they blend]

3) There are a number of other ways to make multiple HSTs at the same time, using the same two fabrics. This gets a bit more involved and might not meet your needs, but if you're interested, either I or someone else can point them out to you.

NOW, as for size...
From what I read, you wish to end up with one giant HST that is 12 1/2" when complete (and 12" when sewn into a quilt), and the same for the 6" one. General rule for HSTs is this: Add 7/8" to the final measurement of your block before you cut...So, for the blocks, you'd cut a 12 7/8" square or a 6 7/8" square to begin regardless of which method you choose to do.

Because many of us wish to trim our finished HSTs to 'perfect' them, we round that 7/8" measurement up to 1" [so you'd cut a 13" & 7" square of fabric]. Then once you're done sewing 1/4" on either side of the diagonal, and press open, you can trim them down to the 12 1/2" and 6 1/2" squares you really need. (This way there isn't any slightly off HSTs that you need to work with.)

Hope this hasn't scared you off. HSTs aren't really that hard and are a wonderful addition to your reservoir...you can do so many things with them and make lots of really complicated looking layouts (that really aren't!)


    Bookmark   July 9, 2011 at 6:49PM
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Jennifer, a big THANK YOU for explaining that to me! Now I'm off to my sewing room to practice, practice, practice!

    Bookmark   July 9, 2011 at 6:55PM
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Jennifer did a great job with explaining the process, now go to it and get started, Dan!!

    Bookmark   July 9, 2011 at 9:06PM
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Dan, congrats on moving forward to triangles! I was terrified of them for a long time too so I understand. Jennifer's advice is great and you won't have any trouble with them. The method she described is the one I believe we all use; it's so much easier than trying to sew on the diagonal!


    Bookmark   July 9, 2011 at 9:56PM
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who knew it could be this easy? I used some jelly roll strips to make a long piece of striped fabric, ironed it (of course), then cut my triangles and re-sewed them into squares...woo-hoo!!! this is cool!!! I'm going to try more HSTs tomorrow!

    Bookmark   July 10, 2011 at 12:44AM
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