A question about pre-wound bobbins...
 

Hoping someone can help me figure this out cuz i cant find any info whatsoever...

my Nolting Quilting Bee (sitdown longarm) uses class “M” bobbins. I recently ordered pre-wound Magna-Glide class “M” bobbins, but due to a backorder of a specific color i received that color in a class “L” bobbin instead. While you obviously cant use a class “M” bobbin in a class “L” situation - is it possible to use the smaller class “L” bobbin in a machine set up for a class “M” machine??? If i sound totally confused - youre right because i am!

Thank you for any light you can shed on this subject!

Don't do it! As small as the differences are, they are great in terms of machine tolerances. One of my friends had a portable Brother that had bobbins that were so close but not quite the same as my friends more expensive set up. Her life got much better once shes threw out all her bobbins and bought new ones. Marking the portable ones with a big black Sharpie X over them and leaving the set-up machine ones plain. I don't remember exactly but I think the wrong ones were the same diameter but just a shade taller/shorter than the others. Both bobbins fit in both machines and both caused problems!

The long arm set-up I used to use also used Type M bobbins. We found we couldn't wind a decent bobbin to save our lives and switched to prewound and vastly improved our stitch quality and happiness level. I think part of that was using a lighter weight bobbin thread than top thread, but a badly wound bobbin causes its own set of problems.

I've heard stories too though about machines that were too particular to use prewounds and the owners could only wind their bobbins on their own machines. I'd much prefer to buy prewounds, and I'm usually too cheap to do things like that. My current machine has an embroidery module but a proprietary bobbin, I know if I ever got an embroidery machine one of the features I would specifically want is a standard bobbin where I could get prewounds.

I have thought of testing this out on my Lizzie but not got around to it yet. You can only try one on a practice sandwich, (manually only) but will the hole in the smaller bobbin be the same as the M bobbin? If the hole is larger you will have a lot of backlash. I know the M bobbin will not fit on the winder spindle of my DSM - I have tried that.

Don't understand why the company would send L size to you if they weren't sure they'd be ok.

No, do not use these bobbins. Have them returned - at no cost to you

Never use a bobbin knowing it is not the exact size your machine demands. It will end up costing you more for repairs and hours of frustration.

I have an Innova longarm and I've used "L" bobbins successfully. (my machine takes "M"). I use the prewound bobbins from Superior thread. I haven't had any problems.
I think you just need to try it and see if it works for you.

I am not 100% positive but I believe Magnaglides use the same size core for both L and M so the only difference is the amount of thread wound on the bobbin core as there are no cardboard sides on magnaglides. I wouldn't be concerned about backlash because the magnetic core keeps it from happening. I am thinking that is the reason the supplier thought it would be ok to send the L instead of the M. Here is a link to their website. They are only open on weekdays but I am sure they or the supplier you got the magnaglides from can confirm this.

https://www.habanddash.com/

Thank you all for your help!

I was able to contact my supplier... and what she told me was essentially what Feline Fanatic just posted. In this case (Magaglide pre-wound) the core for the L and M class bobbins are the same - the M class just holds more thread than the L does.

As another note - I was more than sufficiently compensated for the substitution so everything is good! Just the same, i will do a practice sandwich before starting my next project (which is my practice anyway). I have been assured from the supplier that i can return the L’s for exchange and replacement at no cost to me should i decide not to use them. It will just take another month to get that particular color in the M since they are backordered.

To be clear though... no - do not substitute actual original equipment metal bobbins (L for M - or M for L). That i would definitely not do! As Feline Fanatic reported, the Magnaglide pre-wounds are a different situation. I will update you all once i actually use the L, but it wont be right away because my work-life seems to be getting in the way of my quilting-life! 😊

Thank you all again!

Thanks for the update and do give us a progress report after you've worked with it. Always happy when things work out.

I have both size Magna-Glide prewound bobbins, they both have the same diameter, but the length of the core is longer on the M class. Personally, I would not use them interchangeably on my M class machine, but of course that is me - I tend to error on the side of caution.