The Thread Exchange
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Prewound Bobbin Information

About Bobbins--Sewing machines use two separate threads to sew - a top-stitch that comes from a spool and a bottom-stitch that comes from the bobbin. All machines have bobbin winders that wind the top-stitch thread thread onto bobbins. Unfortunately you must stop sewing while you wind thread for bobbins. Prewound bobbins solve this problem by giving you thread that has been wound to fit your machine's bobbin case. Instead of winding, you just slip a prewound bobbin into your machine's bobbin case and go.

Getting The Right Style -- A bobbin's dimensions (height and diameter) is called its style or type. Each sewing machine is designed to work with a specific bobbin style. So, the first step in bobbin-buying is to identify your machine's style using one of these methods.

  • Consult your machine's manual or your dealer.
  • Get the bobbin style from an old bobbin box label.
  • Use our Bobbin Style Information for Sewing Machines pages to look-up the bobbin style by brand and model. We have information for over 1,600 machines.
  • Match the dimensions of the bobbins that you are currently using to the bobbin dimensions on our Bobbin Style Dimensions page. Dimensions do not include overhangs from paper or plastic sides.
  • Send us a bobbin and we will do our best to identify its style.

Bobbin styles are identified letter (e.g. "A", "G") or numeric (e.g. "37", "58") codes. A given style code will have the same dimensions regardless of manufacturer. There are over thirty bobbin styles currently in use. But, the five styles we stock ("A", "G", "L", "M" and "U") cover 70% of the machines on the market.

BobbinThread Size --The thickness of the thread used on the bobbin is called its thread size. Thread size designations for bobbins are the same as for top-stitch thread. As thread size increases, the thread's tensile strength increases and the number of yards thread on the bobbin decreases. Generally, the bobbin thread should be one size smaller than the top-stitch thread--for example a Size 138 top-stitch would normally use a Size 92 bobbin thread. If you are using a heavyweight thread just for looks, then the bobbin thread might be two or three sizes smaller.

Thread Type -- We sell bobbins made of spun polyester, nylon, and polyester thread. Spun polyester bobbins are used for embroidery and lightweight garment sewing. Nylon and polyester bobbins can be used interchangeably in most cases regardless of the top-stitch thread. There is one very important exception. If you are using polyester thread because you need its superior sunlight (UV) and mildew resistance (e.g. sewing awning canvas) then you should use bobbins made of polyester thread.

Bobbin Quantities - Most of our bobbins come in Gross (144 Count) and Half-Gross (72 Count) boxes. We sometimes have bags of loose bobbins in plastic bags that we sell at great prices.



Prewound Bobbin Information

General information about bobbin styles, thread sizes, side and sideless bobbins, and much more.

Machine / Style Reference

A list of 1,600 machine / models and the bobbin styles they use.


Bobbin size templates for our most popular styles and precise dimensions for the other styles.






The Thread Exchange
291A Merrimon Ave., Weaverville, NC 28787


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