Class 15 bobbin cases are not all the same
Class 15 is probably the most common style in the world, but class 15 bobbin cases are not all the same.
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| Kenmore models 1301 (left) left side loading, vertical hook zigzag, with flat spring releasing thread right into the 11mm x 3 mm needle L slot opening on top of the bobbin case. 1750 (right bobbin case in photo) front loading vertical bobbin hook system Shorter 6mm x 3mm narrow needle opening slot Flat spring releases thread right at the side of the needle opening on top of case. |
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| Singer 15-88 original bobbin case Simanco part # 125291 This is for a side loading, straight stitch only, oscillating hook machine. |
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| 15-88 12 o'clock, left leaning finger position, notice the case door latch is flared, curling out, away from the bobbin case, assisting in stitch formation in oscillating hook machines. |
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| 15-88 flat hinge spring that releases thread at the base of the stitch finger, some other class 15 bobbin cases release the thread at the needle hole. |
Finger can be 11 o'clock, 12 o'clock, or 1o'clock, the finger can slant left, or right. The needle slot may be narrow, or wide, with varying shapes and positions.
The needle opening is critical, not only for stitch formation, but to avoid the needle hitting the bobbin case. Many older zigzag machines have narrower zigzag stitch capability, 3mm, some have wider zigzag, 7 to 9mm.
The flat spring can hold bobbin thread at the top , near the finger, or on the side, depending on the machine's bobbin hook position, some are horizontal, some are vertical, some face the front of the machine, some are side loading.
There are a wide variety of class 15 bobbin configurations, each requiring the correct case, to avoid needle strikes, and to allow full zigzag width to be sewn, without needle strikes.
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| Kenmore 1301 class 15 bobbin case 12 o'clock right leaning finger vertical left loading bobbin hook system, left door latch opening, flat door latch, bobbin fill view window |
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| Kenmore 1301 class 15 bobbin case 12 o'clock right leaning finger vertical left loading bobbin hook system, left door latch opening, flat door latch, bobbin fill view window. Notice quick jam bobbin race cover spring release knobs. |
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| Kenmore 1703 class 15 vertical front loading bobbin hook, 11mm x 3 mm L needle opening slot, 12 o'clock right leaning finger, flat door latch opens left to right, thread fill viewing window opening. Quick release bobbin hook jam fix design |
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