I love hourglass blocks they are super easy to make by joining two half square triangles together and they another good shortcut to learn for the beginner.
The maths to work out what size squares you need to cut is also super easy. Simply Add 1 1/4” to the finished block size ie Cut 5 1/4” square for 4” finished hourglass block or 3 1/4” for a 2” finished hourglass block.
However sometimes I like to add a bit more insurance as I prefer to trim my units before putting them into a block to ensure accuracy so for the above examples I would probably cut 5 1/2” square for 4” finished block and 3 1/2” square for 2” finished block.
Basic Hourglass Block
Prepare all your light squares by drawing a line as illustrated diagonally down the centre of the square.
Place a light 5 1/4” square together with a dark 5 1/4” square, rights sides together and stitch a SCANT 1/4” either side of the diagonal line.
Note: Scant means a few threads less than 1/4” seam allowance. If your final hour glass blocks are bigger they can be trimmed down before they are pieced into the larger blocks.
Using a ruler and rotary cutter cut on the diagonal line.
Press the seam allowance towards the darkest fabric.
Draw and line on the back across the centre of one of the half square triangle units as shown in picture below.
Place the two half square triangles just made right sides together lining up dark fabric triangle against the light fabric triangle.
Stitch a SCANT 1/4” each side of the drawn line. Cut using a rotary cutter and ruler on the diagonal line.
Press two blocks open.
Use a square ruler to square up each of the hour glass blocks. The finished units should measure 4 1/2” square. Line up the 45° angle marked on the square and the 2 1/4” mark with the centre cross of each of the blocks trim along the right edge and across the top of the block. Turn the 180° and trim the last 2 sides until the block measures 4 1/2” square.
Please find instructions for the above quilt Swamp Angel Quilt Pattern.