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Tech Notes, April 2014

April 2014 Service Tip of the Month


Bobbins?  What’s special about a bobbin?  Aren’t they all the same?

Well…no, they aren’t!  There are basically three classes (types) of bobbins out there in the world, with a whole bunch of specialty exceptions. 

Class “15” bobbins
.  By far the most common, both for front, (oscillating hook) machines, and for drop-in machines.  Approximately 13/16” in diameter and 3/8” high.  Available in metal and plastic.  You can use 15 class plastic bobbins in any machine that accepts this type, but you shouldn’t use metal ones in a machine that has a magnetic bobbin system.  You can tell if you have a magnetic bobbin system by the presence of a dark brown ring (the magnet) under the bobbin case in a top-loader machine.  I really like the plastic version in a front-loader machine, because it’s quieter.

Class “L” bobbins.  Just a tiny bit larger in diameter than the class 15, and only 5/16” high.  Available in metal and plastic, but most commonly metal.  A lot of pre-wound bobbins are class L, which sort of makes them universal.  However, since class L pre-wound bobbins are a bit shorter, if you use them in a machine that wants a class 15 bobbin, they will bang around in the case, making noises and sometimes bad stitches. 
Also, if you use a class L bobbin in a class 15 bobbin machine, the bobbin winder may not work.

Class “66” bobbins
.  They are the same height and diameter as the class 15, but the flanges are curved, giving them a domed look.  Available in metal or plastic.  If your machine is a Singer and wants the class 66 bobbin, pay attention, because a class 15 bobbin won’t sew in your machine!

“Specialty” bobbins.  There are a whole bunch of these out there, and my best advice is to be careful to use the correct bobbin the manufacturer specifies.  Singers, including Feather weights and Touch and Sew machines require a specific bobbin for that machine.

Pfaff and Viking machines have used a myriad of these special bobbins, and, for the most part, the machine will only sew with those bobbins.

When Bernina started to use a rotary hook, they changed the bobbin and all those machines require that specific bobbin.  The newer 8 and 9 series Berninas’ also have unique bobbin requirements.

Hope I didn’t confuse you too much here.  Mostly, the message is: take a little care when you buy bobbins!   --------  Boone