Why the right bobbin matters
A bobbin that is slightly the wrong height or diameter can wobble, causing loops, uneven tension and thread jams. Always use the type your machine is designed for.
Common types
- Class 15: one of the most common domestic types, used in many front-loading and drop-in machines.
- Class 66: used in many older Singer drop-in machines; it has a slightly curved face.
- L-style and M-style: common in industrial machines, M being larger for longer runs.
Metal or plastic?
Use what your machine specifies. Some drop-in systems are designed for plastic bobbins and a metal one can affect tension, and vice versa.
Bobbin cases
Front-loading machines use a removable bobbin case with its own tension screw. Drop-in machines have a built-in case. A damaged case causes stitch problems that no amount of rethreading will fix.
Winding a good bobbin
- Thread through the bobbin winder tension disc.
- Wind a few turns by hand, then run the winder at a steady medium speed.
- Stop when full; an overfilled bobbin causes problems.
- Use the same thread on top and in the bobbin for most sewing.
How to identify your bobbin
- Check your manual or the manufacturer’s website for the class or part number.
- Measure diameter and height carefully if you only have the old bobbin.
- Look at the face: class 66 bobbins have a slightly curved face, class 15 are flat.
Industrial bobbins
Industrial lockstitch machines often use larger bobbins than domestic machines, which means fewer changes in production. Make sure you buy the right style for the hook on your machine.
Get a match
Take the old bobbin or the machine’s model number to a specialist. PK Sewing Machines stocks metal and plastic bobbins, cases and rotary hooks for many makes, from its Leicester parts department. See our parts guide, and Leicester’s hosiery heritage for why the city is still a parts hub.
Last updated: 14 October 2026
