Half Square Triangle Tricks – Trimming

Just a quick warning concerning last week’s post. May wrote to say that the “ripper perch” looked a bit dangerous. We should always be careful with any of our tools, but I wanted to assure you that I keep the ripper’s cover on it when not in use.

As I mentioned last week (click here for that post), the center of the quilt that I’m working on contains 336 – 3″ finished half square triangle blocks (there will be more needed for the border). They’re pressed and cut apart and now it’s time to trim.

I find the most time consuming part of trimming is aligning the ruler for every cut. That prompted me to get a Bloc Loc™ ruler – and I’m very happy with it.

This ruler has a groove on the bottom for the seam allowance to nest in.

This means the seams must be pressed to the side. To begin I lined up the Bloc Loc™ groove on the seam, and centered it on the block (I’m trimming my blocks to 3 ½”).

I rotary cut the top and right sides:

Next comes the tricky part. The ruler and block need to be rotated to trim the other sides. I began with a “lazy susan” style cutting mat, but it was awkward and didn’t turn easily. Then I decided to try one of the mini cutting mats in my collection. I found this one spun quickly on my table. It worked great! So here it is rotated:

I simply slid the ruler down the seam allowance to the correct measurements:

and rotary cut the remaining two sides:

The best way to get great points when making half square triangle blocks is to be sure the diagonal seam drops off the block at the exact corners. The groove on this ruler guarantees it!

It’s amazing how long it takes to trim that many blocks, but I am really pleased with how accurate they all are:

After my last post Nancy commented that she likes using the Clearly Perfect Slotted Trimmers™ for squaring up her half square triangles. I’ve watched a You Tube video on them and I think I may need to give them a try – to compare them with the Bloc Loc™. Stay tuned.

5 Opinions

  • Donna K said:

    I LOVE Bloc Loc rulers! They are fool proof. They are great for making HST all the same size..

    They also make many other rulers. One of my favorites is the flying geese rulers. Because earlier I couldn’t make a FG bloc standard to save my life.
    Spray sizing the fabric before hand has greatly helped with my non standard FG blocks of other sizes.

    Bloc loc makes many popular sizes of the FG rulers.
    Downside is that if you are working from a pattern that doesn’t use standard sizes you are still making FG blocks on your own.
    I rarely do anything in standard sizes any more so I don’t reach for the FG rulers too much any more.

    Thanks Chris!

  • Patricia Nieman said:

    I always use the Quilt in a Day square up ruler for trimming. You leave them folded along the seam line and you don’t need to turn them. Both sides are cut at the same time.

  • Linda said:

    Where can I purchase these trimmers? Are they easily found?

  • Cheryl Parker said:

    I’d been meaning to get hubby to drill me a piece of lumber to make a cutter stand, and after your last post, I finally got him to make one. I’ve used a blocloc ruler for ages, and use a 12″ square mat like yours. It turns easily on my cutting table.


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