M bobbin, why 2 types of bobbins?

[Marsha Nichols]

I have the M bobbin and used the bobbin with many holes and finally set great tension on the top and bottom. Then tried the solid aluminum- look bobbin and haven't been able to get good tension on the top.

Why two types of bobbins?

When do you use the holey one and when do you use the aluminum one?

[DawnCavanaugh]

Hi Marsha,

We have two types of bobbins to address different concerns for customers. The ones with the holes are metal, and weigh more. Therefore it takes more force to overcome the inertia to start the bobbin, as well as taking longer to potentially stop the bobbin. Depending on the speed at which you quilt, combined with the other factors such as thread type, batting, quilting direction, etc., can sometimes cause backlashing in the bobbin or railroad tracks on the back side of the quilt.

The aluminum bobbins are lighter weight and are closer in weight to a pre-wound bobbin. They require less force to start them and stop them, and less changes to the bobbin case tension if you switch between winding your own or using a pre-wound. It is more a matter of customer preference instead of one being absolutely better than the other. For years the metal ones were the only ones available, and those are the ones I am personally "used to".

[Marsha Nichols]

Thanks Dawn, so do I need to adjust the bobbin case to get the tension correct for the lighter bobbin? I have loosened the top tension until the stitches are definately loose and then started tightening the top tension to find the sweet spot. So far no luck. The stitches look good on the backing. I might just order more metal bobbins and use them.