What about the under thread?

Top tip: Always clean your bobbin case and check for damage

In this month’s Embroidery Column find out more about under thread and why it is more important than you think, with Jas Purba, managing director of ETC Supplies.

In my experience, most embroidery companies have very little technical reason to influence the choice of under thread they use.

It is normally a case of:

  • This is what my embroiderers like to use.


  • This thread does not break and works without tension or needle changes.

Rather than consider the benefits of different types of under thread available today, this matter is seen as a low priority in the scale of what to use on your embroidery machine.

Let’s consider the two main types of under thread:

  • Pre-wound bobbins.
  • Winding your own bobbins from a spool of thread.


Pre-wound bobbins are available in a variety of different types. These are:

  • Plastic sided bobbins.
  • Card sided bobbins.
  •  Magnetic card sided bobbins.
  •  Sideless bobbins.
  • Magnetic core bobbins.

Most of these bobbins use a polyester filament thread yarn which is thinner than standard ticket 120 under thread and is very strong. The exception to the rule is Coats’ card sided bobbins that use spun polyester thread that is soft and not as strong.

The benefits of using pre-wound are: they are consistent and wound correctly to the right tension. If you do not have a good bobbin winder or stuck for time then these are very good bobbins to use.

The best types of pre-wound bobbins are those with sides. These are used in the bobbin case with the check spring inserted inside. This check spring aids the correct tension and prevents over running of the bobbin.

Sideless bobbins are used by those people who cannot set correct tensions or may be using old bobbin cases. These bobbins are inserted with the check spring removed.

If you have set your tensions correctly, the Coats’ spun polyester bobbins will run perfectly. But if your tensions are set high you will need to use the polyester filament thread bobbins to help combat breakages.

Winding your own bobbins

This allows you greater freedom in your choice of under thread. The bobbins must be wound correctly side to side and with the correct tension. The most common types of under thread are;

  • Spun polyester (ticket sizes 120, 150, 180 and 220).
  • Cotton threads (ticket equivalent 120).
  • Poly/cotton threads (ticket 120 and 180).

The most common thread used in the industry is the spun polyester ticket 120. The higher the number, the finer the thread.

So what is the benefit of using a thinner under thread?

The benefit is you get more thread on your bobbin which means less bobbin changes. Only Gutermann has the technology to manufacture a spun polyester ticket 220 under thread. Large embroidery companies prefer to use this thread as it gives you nearly double the amount of thread on your bobbin. The other benefit is that it is very soft and has a slightly hairy texture that prevents slippage of the thread.

What other under thread is available?

  • 100% cotton thread is rarely used as most people do not know it is available. The benefit of using this thread is that it is extremely soft and will blend into the top thread colour more easily.
  • Poly/cotton threads regardless of wither or not the thread is poly/cotton or poly/poly has no place in the industry to be used as a under thread. This thread – even though, it is very strong and doesn’t break – should only be used on garments that need reinforcement at the seams such as jeans.  To the companies that regularly use this thread as under thread I recommend looking at thread tensions before assuming stronger under thread is the correct option for you.

It may feel like we go on about thread tensions all the time but no matter what you do in embroidery, everything revolves around correct thread tensions.

If your tensions are set correctly you will not have problems with fine designs and you will not have to use several layers of very strong backing. The principle is just the same as a shoe lace. The tighter you pull the laces the more they dig into your feet and the more likely that your shoe lace will break.

Now days you can buy automatic bobbin winders that are extremely fast and efficient at winding perfect bobbins very quickly. You just set up the machine to the correct tensions for your type of under thread. Fill the top up with empty metal bobbins, switch it on and out comes ready wound bobbins in seconds for you to use.

Top tips

  • Always clean you bobbin case and check for damage.
  • Always leave a 2in tail of thread when inserting the bobbin into the case.
  • The bobbin should be placed so it runs clockwise, the thread unwinds off to the right.
  • Feed the bobbin thread through the notch and into the hook.
  • Twist the bobbin thread twice around the pigtail.
  • When pulling the thread the bobbin case turns the opposite direction.
  • Use a tension gauge to set the correct tension on each bobbin case. Pre-wound bobbins have a tension setting of around 100 and metal bobbins have a setting of about 200.
  • Carry out the stitch test on one head to get the one third under thread showing. When you have the correct tension for this head you know what tension to set the other heads.

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