Special Notes About Rotary Cutting

Rotary cutting dimensions are nearly always approximations. For example, the ⁷/₈ inch that quilters conventionally add for half-square triangles is really .85355 inches, rounded off to the nearest ¹/₈ inch so that we can read it on the ruler. Experienced quilters in fact cut a little "shy" in this case, since .85355 is a little less than ⁷/₈.

This applies, of course, to the dimensions given in Quilt Design Wizard™ rotary cutting printouts. Here are some things that you should know when deciding on the best type of pattern to use for a given block.

1 Quilt Design Wizard™ gives the conventional results.

In simple cases, rectangles and triangles in even sizes, for example, Quilt Design Wizard™ gives the same results as conventional quilter's wisdom. It adds 1¼ inch to the finished size of quarter-square triangles, for example, just like the books.

The inaccuracies produced by rounding off can become significant if the finished sizes of patches are not easily measured on common rulers. This block has 7 patches across by five patches down. If you wanted a 10 inch block, this would mean that each rectangle has a finished size 1.43" by 2". 1.43 is not to be found on your ruler.

Quilt Design Wizard™ would add the ¼ inch seam allowance, round off (say, to the nearest ¹/₈ inch), and tell you to cut rectangles 1⁷/₈" by 2½". If you then pieced together these pieces (assuming you use accurate quarter inch seams), the finished size of the actual block would come out to be 9 ⁵/₈" by 10, a full ³/₈ inch too narrow!

2 Templates may be used as a check.

Quilt Design Wizard™ templates are always accurate. If you are uncertain about rotary cutting dimensions in some case, print the templates as a check. The actual (unrounded) dimensions for rotary cutting may be measured from the dotted (seam allowance) lines on the templates. First extend the dotted lines until they cross. Then measure the resulting total length and height.