prewound bobbins
Information Topics
Bobbin Buying Guide
Why Buy Bobbins?
The Right Style
Bobbins and Thread Size
Bobbins and Thread Type
What Is A Gross?
Machine / Style Reference


Bobbin Buying Guide
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, and 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 you are currently using by downloading our Bobbin Style Dimensions (PDF) page.  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 Bobbins - A.KA Class 15 Bobbins
style a bobbins Style A bobbins are typically used with home, and small commercial machines for garments and embroidery. There are some industrial machines that also use this bobbin. Its diameter is approximately that of a U.S. penny, and its height is approximately 8 pennies stacked. Dimensions
Diameter: 13/16" (0.815 In.), 2.070 cm
Height: 15/32" (0.465 In.), 1.181 cm
Print Actual Dimensions: Click Here (PDF)

Forward - Style G and Style L Bobbins - Very close, but much different
style g bobbins Style G (left) and style L (right) bobbins are very close in size. Both bobbins have about the diameter of a U.S. nickel, but style G bobbins are taller. They are not interchangeable.
Style G bobbins are usually used in small to mid-sized commercial machines, and style L bobbins are the most common bobbin used in home sewing machines.

Style G Bobbins
style g bobbins Style G bobbins are typically used in small and mid-sized commercial sewing machines for sewing garments, fabrics, leather, and upholstery. Its diameter is approximately that of a U.S. nickel, and its height is slightly taller than 5 nickels stacked. Dimensions
Diameter: 55/64" (0.861 In.), 2.19 cm
Height: 25/64" (0.39 In.), 0.99 cm
Print Actual Dimensions: Click Here (PDF)

Style L Bobbins
style l bobbins Style L is the most common bobbin style used in home sewing machines. Its diameter is approximately that of a U.S. nickel, and its height is slightly shorter than 5 nickels stacked. Dimensions
Diameter: 27/32" (0.837 In.), 2.13 cm
Height: 23/64" (0.359 In.), 0.91 cm
Print Actual Dimensions: Click Here (PDF)

Style M Bobbins
style m bobbins Style M bobbins are normally used with mid-sized and large commercial machines for heavy fabric, canvas, upholstery, and leather. Its diameter is slightly greater than a U.S. quarter, and its height is just barely taller than 6 quarters stacked. Dimensions
Diameter: 1-1/64" (1.02 In.), 2.60 cm
Height: 7/16" (0.435 In.), 1.10 cm
Print Actual Dimensions: Click Here (PDF)

Style U Bobbins
style u bobbins  Style U bobbins are typically used with heavy duty commercial machines for sewing thick fabric, upholstery, and leather. Its diameter is about the same as the less common Sacagawea Dollar coin, and its height is just shy of 6 Sacagawea coins stacked. Dimensions
Diameter: 1-3/16" (1.181 In.), 3.00 cm
Height: 29/64" (0.457 In.), 1.16 cm
Print Actual Dimensions: Click Here (PDF)

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. Using a thinner thread size means more thread per bobbin, and fewer change ups.

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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