HST Seam Allowance Piecing Tip

Half-Square Triangle (HST) Piecing Tip

To celebrate the Triangle Transparency quilt pattern release, I want to share a half-square triangle (HST) piecing tip that helped me chain piece the quilt top together quickly. The Triangle Transparency quilt studies transparency using an overlay of triangular shapes. Block construction is achieved using Half Square Triangles (HSTs) and strip piecing to quickly create a 60″ by 60″ lap quilt.

HST Seam Allowance Piecing Tip

HST Seam Allowance Piecing Tip

There are several different methods to make HSTs, and I prefer to create oversize units and trim them back to their exact unfinished size. I have found this allows me much higher piecing accuracy during block construction. The method I am going to describe creates 2 HSTs of one color combination at once and is the basis for the cutting instructions in this pattern.

HST Step 1

Place (2) fabric squares right sides together with the lightest fabric on top. On the wrong side of the lightest fabric, mark one diagonal line from corner to corner.

HST Step 1

HST Step 1

HST Step 2

Sew a quarter inch seam allowance on either side of the marked diagonal line. BEFORE you mark extra lines to sew along to create your quarter-inch seam allowances, check out the tip below!

HST Step 2

HST Step 2

HST Seam Allowance Piecing Tip

Tip: Check to see if moving your needle all the way to the right and sewing with the marked line centered creates a scant quarter inch seam allowance.

Seam Allowance Tip - Move Needle All the Way to the Right

Seam Allowance Tip – Move Needle All the Way to the Right

The first thing I tried was moving my needle fully to the right and sewing as normal with the marked centerline going down the middle of my presser foot. This created very scant quarter inch seams.

Seam Allowance Tip - Adjust Reference Point for Sewing Down Centerline

Seam Allowance Tip – Adjust Reference Point for Sewing Down Centerline

The next thing I tried was to adjust the reference point that I used to sew down the marked centerline. Instead of keeping the marked centerline centered under my presser foot, I used the inside “notch” on the left hand side of the presser foot as a guide.

Seam Allowance Tip - Note I Sew on a Bernina and Used Foot 1D

Seam Allowance Tip – Note I Sew on a Bernina and Used Foot 1D

As a reference, I sew on a Bernina and used my 1D foot.

Seam Allowance Tip - Quarter Inch Seam Allowances

Seam Allowance Tip – Quarter Inch Seam Allowances

The offset needle in combination with offset reference point for sewing along the marked centerline created beautiful quarter-inch seam allowances and reduced the amount of time I spent preparing my fabric squares for piecing!

HST Step 3

Cut into (2) triangles along the marked diagonal line.

Tip: Iron the blocks to set your seams prior to Step 3.

HST Step 3

HST Step 3

HST Step 4

Press the HST seams open. Trim square to the desired unfinished size.

Tip: Use a square grid ruler with 1/2″ grid increments to make trimming HSTs to size quick and easy.

HST Step 4

HST Step 4

Tips and Tutorials Tuesdays

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17 thoughts on “Half-Square Triangle (HST) Piecing Tip

  1. Woohoo!! I see an orange Triangle Transparency coming our way! 🙂 I have found that using my quarter inch foot gives me great HSTs. I use the side guide and align it with the drawn line. I’m probably not explaining it very well, but it works for me.

  2. This is my favorite way to make HST too, I oversize and then trim (I use a block-loc ruler which makes the trimming go pretty quickly).

  3. Diana says:

    Good tutorial~and I have 3 of those orange fabrics in my stash…why does having the fabric someone used make me…happy? 🙂

  4. Terri Ann says:

    I do the same thing Beth described using my 1/4″ foot (the one that doesn’t have the edge piece) and that way I can still use my straight stitch plate.

  5. kittywilkin says:

    Hmm I think I should play with moving my needle more. We used this method in Cheryl Arkison’s class at QuiltCon and it seemed to work pretty well once I got the hang of it. Thanks for the tip! I also like to make my HST large and trim down. That way the actual corner to corner sewing doesn’t have to be SOOO perfect, and it makes it all go so much more quickly.

  6. Lynda H says:

    Somewhere I read a tip that advised to trim your HST’s before pressing them open (you can also trim those dog ears) – I am curious to know if anyone out there does this – makes some sense to me.

  7. Renee says:

    Oh this is a good idea! I use my 1/4″ foot with the guide, and move the needle over a skeenth (technical term I got from Jim that basically means the width of a saw blade, but for sewing means 1/16″-1/8″) so I’m sewing at a scant 1/4″ from where the guide runs along the drawn line.

  8. Great tip!
    I will try this out soon!

  9. Shauna says:

    I prefer oversizing and trimming down too. I love your Triangle pattern, it is going to have to go onto my to do list. 🙂

  10. Jasmine says:

    Very similar to what I do. 🙂 I liked seeing how you used a different foot. I usually use my quarter inch foot.

  11. Vera says:

    I haven’t noticed the HSTs in your pattern until now 🙂 What a great construction!

  12. Michelle says:

    How have I done so many HST’s and never thought to move the needle over? I will have to check out your triangle pattern!

  13. Judy says:

    O.M.G. Yvonne! This is awesome!! I had never thought of moving the needle. Such a simple thing, but not (I would have never thought to do it)! LOL Thank you, definitely going to try this out!

  14. sally says:

    I think I need to make something with HSTs in the near future now, everytime I see them I just think again how versatile they are.

  15. Oh how I LOVE this tip! HST are so diverse and this is PERFECT! I am getting used to using a scant 1/4” instead of a true 1/4” seam as this has been proven to be my issue with blocks coming out slightly off. Thank you for the tip!

  16. Brenda Ackerman says:

    I really enjoyed reading this tutorial! What a fabulous idea. Thank you for sharing.

I really appreciate the time and thought you take to comment, and I look forward to conversing with you. :)