The Bobbin Buying Guide gives information needed to buy the right prewound bobbins. We approach this by helping customers decide if the time saved is worth the cost. Then we discuss bobbin styles, thread size, and thread type. There are links to our Bobbin Style Dimensions download that has style / size templates for the five most popular styles, an our Machine / Style Reference that identifies bobbin styles for over 1,600 machines
Why Buy 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.

Bobbins are expensive compared to using thread from a spool. Using them comes depends on how you value your time. Here is one approach:

  • Estimate the time it takes to wind bobbins.
  • Put a value on that time.
  • Multiply time spent by the value of your time.
  • Compare the result to the cost of prewound bobbins.

Buying 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.
  • Match the dimensions of the bobbins that you are currently by downloading Bobbin Style Dimensions page (right). Dimensions do not include overhangs from paper or plastic sides.
  • Use our Machine / Style Reference pages to look-up the bobbin style by brand and model. We have information for over 1,600 machines.
  • 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.

Style A Style G Style L Style M Style U
Style A / Type 15 bobbin compared to U.S. quarter Style G Bobbin compared to U.S. quarter Style L bobbin compared to U.S. quarter Style M bobbin compared to U.S. quarter Style U bobbin compared to a U.S. quarter
Used with home, and small commercial machines for garments and embroidery Used with small and mid-sized commercial sewing machines for garments, fabrics, and leather. Used with home sewing, embroidery, and small commercial machines for embroidery and garments Used with mid-sized and large commercial machines for heavy fabric, canvas, upholstery, and leather. Used with heavy duty commercial machines for sewing thick fabric, upholstery, and leather. 

Bobbins and Thread 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.

Bobbins and Thread Type -- We sell bobbins made of spun polyester, nylon, and polyester thread:

  • Spun polyester bobbins are used for embroidery and lightweight garment sewing.

  • In most cases it does not matter if the bobbin thread is nylon or polyester. If an item is used outdoors, use polyester thread because of its better sunlight (UV) and mildew resistance.

What Is A Gross? - Bobbins are sold by the number of bobbins in a box. Most manufacturers sell by the gross - an infrequently used term that means the box has 144 bobbins. Some sell half-gross boxes with 72 bobbins.
Machine / Style Reference - We list bobbin styles for over 1600 sewing machines and models with one-click links to our bobbin style pages.

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