I've had a few questions over the years as to what size ruler to use for orange peel or continuous curve designs in squares of piecing, usually with someone asking for a ruler recommendation for a particular sized block.
It's quite a difficult question to answer with words, or at least explain the 'why' of the answer. But today, I just felt like giving this question a fuller explanation and since it's longer than really can fit in the Q&A portion of the Craftsy platform, I figured I'd tackle it here. (Of course leaving a link in the class platform.) So here goes....
Q: What size ruler do I need for an orange peel design on a field of 4 inch blocks?
A: It depends.....
See? That's why it's hard for me to answer in words! If I were a ruler making company, I'd probably tell you exactly what size, or sizes for each block size, and a handy link to buy said rulers. That's why my second Craftsy class (instructor affiliate link) is all about making the most out of rulers you may already have.
I do have a shop that I sell rulers from, but I'm first and foremost a quilter, and the frugality that's been a huge part of my life as a stay at home mom and now, as a small business owner makes me leery of adding stuff if I don't need it. But IF I think I'll use it, I do love having the right tool for the job! (Anyone needing proof of that can look at my car and then look at my wonderful Janome 15000 and see where my priorities are....ahem.)
I managed to work up the following graphics to illustrate my point. For a series of 4 inch blocks, it might seem like the answer is a circle or arc that reaches across the corners of that block, or whatever sized block.
The problem happens when you realize that the desired circle would have the same diameter at the diagonal of that square. In the case of the 4 inch square, having brought out my long neglected Pythagorean theorem, is that would be a circle measuring 5.66 inches. Which you aren't going to find a ruler in that size, not even an arc (arc rulers have the same sized curve as the circle they are named after).
The more likely measurement is to use an arc or circle (I prefer arcs when you go to larger sizes, BTW.) for twice the size of the block. This gives you the orange peel in a diagonal orientation which is the traditional orientation of the orange peel block.
But what if you don't necessarily want that diagonal orientation? Maybe you are going for more of a "continuous curves" design? The diagram below* shows some different options. In my second class with Craftsy, I show how you can play around with the rulers you may already have to test sizes and blocks on your quilts to see if they will work for the design you have in mind.
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| *Partial patterns shown for clarity's sake. |
In blue you'll see how a larger arc or circular ruler might look going from corner to corner. You lose that rounded shape to that of a more squared off shape, but the effect is still pretty fabulous.
In the green are 4 inch circles. You can see that they dip in too far to work corner to corner, but would work in a diagonal overlap for 2 inch squares or for completing the entire orange peel within the 4 inch shape.
Whew! There's my exhaustive (exhausting?) explanation of what seems like a simple question. I hope this helped.
system) The Post Its were put into my bullet journal. Here's a 
while quilting just to help where the insert and machine joined and to cover the two support screws to the left of the machine opening. The table is pretty small for using to quilt more than a table runner or topper. It's perfect for samples or piecing. Using regular tables against it to expand the surface should be useful for supporting a larger quilt. I also found it the perfect height for sitting in a regular chair at the quilt show. I had my own sewing chair in the car since I hate being too low or too high at the table while machine quilting, but I didn't need to use it.
or 
shank) plus the 
) worked on their Brother machines.
