Somebody recently asked how to cut tumbler blocks and since I've done this quite a bit, I thought I would post a quick tutorial on how to quickly cut these quickly and easily. I've never posted a tutorial on my blog before, so hopefully it makes sense.
Tumbler blocks are essentially a square block with two 60 degree angles and two 120 degree angles instead of four 90 degree angles.
The basic unit looks like this. The four sides of your blocks are all equal length. The height of your block is equal to your side length times 0.8660. This is useful when mass cutting blocks as I will demonstrate below.
Enough with the math! Let's cut!
I want to cut blocks with 3" sides. I can strip cut these with a ruler using a 60 degree line. First I cut strips. To get the strip size I take
3 x 0.8660 = 2.598
Using my handy conversion chart, I select the number closest to my result. In this case the closest measurement is 2 and 5/8 inches.
(I prefer not to measure down to the 16th of an inch, but the choice is yours).
Taking my fabric I cut a 2 5/8 inch strip.
Using a ruler with a 60 degree line, I line it up on my fabric strip and begin cutting. I like to mark just above my 60 degree line with painters' tape to ensure that I am using the correct line as I cut.
(If working on a large project, you can stack several strips to cut at the same time.)
Make the first cut on the left side of the fabric, as your starting point.
Move your ruler over 2 5/8 inches** and make your second cut.
**NOTE that this measurement is equal to your strip width and you will need to adjust if using different sized strips.
Keep cutting until you have cut the entire strip.
The result will be blocks that can be sewn into tumbler blocks like this.
This method is also very useful if wanting to sew offset triangles to a square of a certain size.
I have a 4" inch square that I want to sew 60 degree triangles to to get something resembling this.
My squares are four inches so:
4 x 0.8660 = 3.464 or 3 1/2 inches
I cut a strip 3.5 inches wide.
Marking the 30 degree line on my ruler I line up the diagonal line on the straight end of my strip. The bottom edge should be half an inch wide regardless of the size of the finished triangle. This is your seam allowance. On my ruler this approximately lines up with the 11" straight line.
After cutting the first triangle, flip the ruler over from top to bottom and left to right.
The ruler will now be inverted.
The top will now need to reflect the half inch seam allowance. Cut along the straight edge.
Continue to cut in this manner down the entire strip.
When finished you will have a block that looks something like this.
(Because of the small amount of rounding, I always square up my blocks when using this method before moving on.)
Have fun!