Wow, my ignorance on things sewing abounds, even after more than 60 years' experience! I just bought some Aurofil 50 weight cotton for bobbins, so apparently what I have been using is 40 weight ordinary thread? And now I hear 60 weight is even better? Yikes, there's always more to learn (for example, it was only a couple of years ago that I found out there were different size needles. . .). I must be a senior member based on age, not skill!