I did some experimenting this AM, before going further with my Ocean Waves project.
I tried a few different feet, sewing together 3 - 2” strips. Once sewn and pressed (I pressed these all open because I’m using open pressing for this quilt, although I don’t always), they should measure exactly 5”. That’s 2” x 3 = 6”, minus 1/2” for each of 2 seams, = 5”.
I didn’t get a single one that measured 5”! The compensating presser foot* and walking foot both take exactly a 1/4” seam, which results in a small loss, even with open pressing, so both of those measured about 1/16” shy of 5”.
The regular presser foot that came with the machine takes a VERY scant 1/4” seam, so with that one I got about 1/16” more than 5”.
I am using Guttermann cotton thread.
You can see on each presser foot, I placed the red ruler, which has a hole at 1/4”. Both the compensating presser foot and the walking foot measured right at 1/4”, but the regular foot, as you can see, was narrower.
Interestingly, the 1/4” marking on the throat plate is too wide. I don’t usually use those anyway. I wonder if that was because the machine is Japanese and was converted from metric, if they didn’t use a very precise conversion.
I have 3 feet from Ebay on the way, plus my acrylic foot from the Janome, to also compare. But it’s looking like I might be best off just continuing to use my regular foot for this project, since I already started and the at least my blocks will all be the same inaccurate, rather than different and inaccurate. :)
The 3 feet above came with my Juki.
*The compensating presser foot has a guide on the right that prevents you from sewing a larger than 1/4” seam. But, it also means that the fabric must be flush with that side. For example, you can’t make HSTs using the drawn line method, because the foot won’t sew over the middle of fabric. It has to be along the edge only, and even little triangle points or threads won’t go through.