Using exactly the same thread (top and bottom) and needle and fabric in each machine, do the stitches look better on one machine than the other?
That bobbin thread looks thick on my screen. If it is, it would create a large obstacle to wrap around, giving the look of a twist much more than a thin bobbin thread.
I.e a 60wt cotton top going around a 40wt cotton bobbin thread would look more twisted than a 50wt around a 50 wt - another good reason to match our threads.
(You knew I'd have a "discovery assignment, right?
)
I can make a FW or 301 stitch "crooked" by doing the same thing. The stitches will line up with a ruler, but look twisted.
hmmm. Another blog post idea.