How to sew equilateral triangles - a tutorial

As regular readers will know, over the last little while, I made two quilts featuring lots (and lots) of equilateral triangles.  

I have already done a tutorial on cutting equilateral triangles, and thought it might be useful to put something together showing my method for sewing them together.  Here goes!

First, line up the triangles you want to sew together.  I strongly recommend that you line the triangles up with the grain kept straight, unless a design decision dictates otherwise.  If you keep the grain straight, once you sew the triangles together in rows, all your bias edges will be stitched up and there is less chance of your strips warping.

The arrows indicate the direction of the grain

 Then, flip one triangle over so that two rights sides are touching.

Pin along the seam line.

Sew a quarter inch seam using your preferred method (I like using my quarter inch presser foot).

Remove pins and finger press the seam open, focussing on the corner that touches the next triangle to be added.

Turn your sewn piece right side up and slot it back into your layout.  Flip the next triangle over so you have right sides touching.

Pin along the seam line like before.

When you are pinning, if you can get one pin through the seam, it will really help keep the seam open.

Keep stitching your triangle pieces together so you have two strips.  For the end square up pieces, make sure that the top straight edge is at least half an inch wide.  If you make it exactly half an inch, you won't need to square up the edges, but as long as it is at least half an inch wide you will have enough fabric to square up and have a seam allowance so you don't lose the points along the edges.

Once you have stitched all your triangle pieces and end pieces together into strips, you should have something that looks like this:

Pressing time.

I like to press hot and with lots of steam.  To avoid the steam warping the bias edges, I finger press the seams open and then just hover the iron over the seam so it is just touching.  I find the seam just folds out flat with little effort.  I like to use the residual heat in the ironing board after I have pressed one seam to help with finger pressing the next seam.

Now it's time to sew your rows together.  Pin the rows together with the points aligned and sew a quarter inch seam. 

 Press the seam open...

...and bam - nice equilateral triangles.

So, that's how I do it.  I'm sure there are other (possibly better) ways, but this works for me.  Please let me know if you have any questions - I am happy to answer via email and will update this post if I think the answer will be of general application.

Finally, I thought I would do a little demonstration to show why I cut the corners off all the equilateral triangles.

Little extra flappy triangle bits.  Bulky seams.  Need I say more?