Proportion Scale Wheel

This is an odd tool that I use in my sewing room. It is my old proportion wheel from the days when I did technical illustration. Handy tool, this.

Why did I use this when I have quilting software that will do the job for me? Because I am not making a quilt. I am making a Schlepp Bag and have adjusted the size of the squares. The pattern calls for 8" squares but the pant legs of the blue jeans I am using only allowed for 6" squares. The first time I made this bag I followed the pattern explicitly and I found the bag to be a bit too big for my tastes, so cutting 6" squares will work fine.

It was easy to convert all the other measurements until I got to cutting the lining. Um, the pattern called for 22.25" squares. What do I cut?

I started with my known measurements: 8" and 6". I lined up the 8" mark on the inner wheel with the 6" mark on the outer wheel and came up with a 75% reduction (see in the little window?). Follow the markings around the inner wheel until you come to 22.25". It lines up with 16.75". THAT is the measurement of my new lining square.

I think, though, that I'll cut the easier number of 17" and then just deepen the seam. After all, it is the lining and a deeper seam will help. Or I could cut it off by sergeing the seams.

I love this wheel; is is well used. Can you see where I've scratched in the smaller numbers of .25", .5" etc? It covers from .12" all the way up to 90". If you put the smaller number on the inner wheel and the larger number on the outer wheel, then you are enlarging. Cool, huh?