On Point Quilts the Maths

the Set in triangles in Nth and Sth | On Point QuiltsAbove is my example of  on point quilts. I called it ” North and South” and it will be in an upcoming issue of Handmade it may be even the next issue, I’ve kind of lost track. It was called “North and South” because at the time of its creation I was binge watching North and South on Netflix and reading the novel it is based on by Elizabeth Gaskell.

The blocks just begged to put on point and the beauty of the cutting technique for the set in triangles meant that I fully utilise the Tula Pink directional fabric and was able to have octopi upright along all four sides of the quilt with no waste.

Set in triangles the maths of On Point Quilts

Set in triangles must have the straight grain along the outside edge. If you fail to do this, your quilt top edges will stretch and it will never be square. To ensure that the outside edge of the triangle is on the straight of grain you need to cut a large square and sub cut it on the diagonal twice to get your Set In Triangles.

Diagram for cutting set in triangles

To calculate the size of the square you need to cut first calculate the diagonal measurement of the block. To do this times the finished size of the block by 1.414 then round that number up to the nearest 1/8th of an inch.

For example for 12” blocks the maths is: 12” x 1.414 = 17”

To calculate the required square to cut add 1 1/4” to this measurement. Therefore you will need to cut 18 1/4” Square. From this you will get 4 set in triangles. If you want quilt to float in the centre add another 1/2” to the measurement and your blocks will be set in slightly from the border edge. Cut the required number of squares needed to give you enough set in triangles for the quilt you are making.

Corner Triangles more maths for On Point Quilts

These are cut on the diagonal once.

To calculate the required square. To calculate take the finished block size and times it by .707 and round up to the nearest 1/8th then add 7/8th of an inch.

12” x .707 + 7/8 = 9 3/8.

Cut 2 squares 9 3/8” cut in half on the diagonal.

Join the rows together on the diagonal and add the corner triangles last. Remember if you have added to the set in triangles so that they float you may need to adjust the corner triangle calculation.

Amanda Bergamin

About Amanda Bergamin

Amanda has been quilting for 20 years and sewing most of her life having learnt from her mum and nana. She started Seabreeze Quilts about 5 years ago designing patterns for her etsy shop. Her favourite technique is needle turn applique, but she also uses machine applique, machine quilting (she quilts all her own quilts usually by machine) and machine piecing. No matter how long Amanda has been quilting she know the value of classes and learning from others. As well as teaching beginners classes, Amanda always makes sure to take at least one or two classes a year, as there hasn’t been a class she has attended where she has not learnt something new from the teacher or other students. Over the last two years she has run a free BOM on her blog seabreezequilts.blogspot.co.nz. Patterns for the month are available for free then up for sale in her etsy shop https://www.etsy.com/au/shop/seabreezequiltsoz for a small price so you can catch up if you want to join in.

Leave a Comment