Tuesday, March 18, 2014

Tip Tuesday! - Math for Quilters, Part 2

Tip Tuesday! -  Math for Quilters 

It Doesn't Have to be the "M" Word - Part 2
Side Setting Triangles and Corner Triangles

Welcome to

"Tip Tuesday!"

I love learning new things and then sharing that knowledge with my quilting friends. So, every Tuesday I'll provide some tips, hints, tricks, tutorials, shortcuts, etc. that I've learned over the years and share them here on the blog. 

"Tip Tuesday" will be a collection of information about a wide variety of subjects garnered from a large variety of sources.  I am not an expert by any means and do not take credit for being the great wizard behind all of these hints and tips. I will gladly give credit where credit is due whenever possible.
These tips will be archived and accessible to you just by clicking on the "Tip Tuesday" tab above. 

Read, enjoy, and be inspired! 

Last week, I shared some basic math stuff, like a yardage chart, fraction/decimal/inches conversion, standard mattress sizes, etc. and I promised to discuss side setting and corner triangles this week. 

Now I know that most on-point or diagonally set quilt patterns will tell you what size to cut the squares in order to get your side and corner triangles, but often they are cut to the exact size and if your piecing is off even a little bit, that can result in a stretched seams or bowing corners. To avoid these problems, I usually increase the starting cut square at least 1/4" and trim as needed once the triangles are attached to the quilt. 

But, what do you do if you are designing your own quilt or enlarging an existing block? I hate to say it, but you must do some math. Have no fear though, it is very simple math. (It's trigonometry, bit it's still simple!) 

I'll start with a very basic explanation of on point (diagonal set) quilts and the math (with examples) will follow.

On Point (Diagonal Set) Quilts
When you place blocks on point, also called a diagonal set, you need to fill in the outer edges of the quilt with triangles. The triangles along the sides are called side setting triangles. Corner setting triangles fill in the corners of the quilt.

Calculating Side Setting Triangles
1. Multiply the finished size of the block by 1.414 (round up to the nearest ¼”)
2. Add 1 ¼” to that number
3. Cut a square equal to that number
4. Cut the square twice on the diagonal (corner to corner)

Example: finished block = 6”
1. 6” x 1.414 = 8.484  -- round up to 8 ½”
2. 8 ½” + 1 ¼” = 9 ¾”   (8.5 + 1.25 = 9.75)
3. Cut square 9 ¾” and cut twice on the diagonal (corner to corner)

4. Use the quarter square triangles as side setting triangles

Calculating Corner Setting Triangles
1. Divide the finished size of the bock by 1.414 (round up to the nearest ¼”)
2. Add ⅞” to that number
3. Cut a square equal to that number
4. Cut the square once on the diagonal (corner to corner)

Example: finished block = 6”
1.  6 divided by 1.414 = 4.24 (round to 4 ¼”)
2. 4 ¼” + ⅞” = 5⅛”  (4.25 + .875 = 5.125)
3. Cut square 5 ⅛” and cut once on the diagonal (corner to corner)

4. Use half square triangles for corner setting triangles

I love the look of diagonally set quilts and used to be afraid of them, but not any more. Once I figured out the math and did it a few times, it was easy. 

I hope this helps! Feel free to ask questions.

1 comment:

Anonymous said...

I really needed this! It' like having a private lesson! now I can finish one I've been waiting on to learn how to do it-