How to Make Half-Square Triangle Quilt Blocks
Five Methods for Fast and Accurate Piecing
Apr 24, 2009
A half-square triangle block consists of two right triangles of fabric, usually one lighter and one darker, sewn together into a square along the diagonal edge.
Half-square triangles are an essential element in literally hundreds of favorite quilt blocks: Pinwheel, Friendship Star, Churn Dash, and Shoo-Fly, to name just a few. Half-square triangle blocks also make good supporting players in a quilt, helping to frame a central design or add interest to a dull border.
There are many ways to make half-square triangles. The techniques described here are some of the ones quilters use most often.
How to Size Fabric for Half-Square Triangle Blocks
Adjusting for seam allowances means you will need to start with a piece of fabric larger than the finished block. If you are a very accurate sewer, start with a square of fabric 7/8” (0.875 cm) larger than the block’s finished size. If you are a beginner, you may want to add 1” (2.5 cm) to the finished size, then trim to the correct size after you sew. That way, you don’t need to worry about accidentally making the blocks too small.
Cut and Sew Half-Square Triangle Blocks 5 Different Ways
- Cut two same-size fabric triangles and sew them together along the diagonal edge. If you use this technique, be careful when you handle the triangles, especially when you feed them into your sewing machine. The long edge of each triangle is a bias edge, which makes it harder to sew without stretching and distorting the fabric under your sewing machine’s feed dogs.
- Make two half-square triangles at a time from two fabric squares.This is an easy, popular method and the best one when you are making scrappy half-square triangles from lots of different fabrics. To speed up block construction, chain piece the blocks when you sew. See the second photo below for step-by-step instructions.
- Use a grid marked on a large piece of fabric to mass-produce identical half-square triangles. This method is good when you want to make a lot of triangle blocks at once from the same two fabrics. Some quilters report that the sheer number of seams tends to shrink the blocks, though.
- Strip piece with special half-square triangle rulers or templates. The WonderCut ruler, Easy Angle Ruler, Marti Michell template set, or Omnigrid 96 ruler are all designed to speed up piecing on half-square triangles.
- Foundation or paper piece half-square triangles. This method is best when you want absolutely precise points and seams, or if you are making miniature blocks. You can use standard paper piecing techniques or buy one of the many specialized foundation papers for creating half-square triangles, such as Thangles, Triangle papers, or Triangles on a Roll.
Each of these piecing techniques has its own unique advantages and disadvantages. If you’re new to quilting, why not try them all? That's the best way to find out which techniques fit your way of working.
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