A few days ago, I took us all back to basics with a post on trimming Half Square Triangles. Except, right in the middle of it I taught you how to cheat! The cheat instructed you how to trim HSTs without rotating for every side, essentially saving a little bit of time by cutting two sides at a time and only rotating the piece once between the second and third trim.

I did include a warning regarding the danger of the method, as its more likely to result in losing control of your rotary blade. What’s the worst that could happen, you ask? Well you could accidentally slice into the piece you are trying to trim, rendering it useless. Or even worse, you could accidentally cut yourself. Trust me, I have done it and I’ve seen other skilled quilters and sewers do it as well.

Today, I would like to redeem myself as a teacher, and show you the safest way to trim HST. So, let’s try again, this time without cheating. Imagine you have already pressed your HST and you are all set to cut. Once again, you will align the diagonal line on your cutting ruler with the diagonal seam, careful to protect (under the ruler) more than what is needed for your final dimension. I always start with my diagonal running from lower left to upper right ( like a forward slash / ). You make the first cut.

HST Trimming

The first cut will trim the excess grey fabric to the right of the ruler using the / diagonal.

Then rotate 90 degrees clockwise, realign the ruler with the diagonal running from upper left to lower right (like a back slash \ ). Once again you will cut on the right side of the ruler. Notice that the first cut now aligns perfectly to the bottom edge of the ruler and the diagonal points directly to the corner. Make your second cut.

HST Trimming

The second cut will trim the navy floral using the \ diagonal

Once again rotate the fabric 90 degrees clockwise. This time you will align the diagonal ( / ) as well as the left edge of the fabric with your final cutting dimension. So in this case, I aligned the left edge at 2 1/8″. Make the third cut.

HST Trimming

Ready for the third cut, trimming the navy floral print using the / diagonal

At this point it’s easy to see that you have one side left to trim in order to square the piece at 2 1/8″.

Notce the extra lip of grey fabric past the lower point of the diagonal seam.

Notice the extra lip of grey fabric past the lower point of the diagonal seam.

After a final 90 degree rotation, the diagonal ( \ ) alignment should direct your edge alignment to the final cutting dimension. Make the fourth cut.

The fourth cut, after rotating again we are once again using the \ diagonal.

The fourth cut, after rotating again we are once again using the \ diagonal.

So today’s Back to Basics lesson used exact steps to carefully and precisely trim your HSTs. Again, the additional rotation is a wise move when you are concerned with maintaining control of the rotary cutter and ruler as you will always cut directly away from your body, instead of across the body.

HST Quilt Trimmings
Happy trimming!