# Machine embroidery thread explained

Source: https://stitchandhem.co.uk/blog/machine-embroidery-thread-explained
Published: 2026-10-12
Publisher: Stitch and Hem

**In short:** Most machine embroidery uses 40 weight polyester or rayon thread on top and a finer 60 to 90 weight bobbin thread underneath. Polyester is stronger and more colourfast, which suits clothes that are washed often; rayon has a soft, high sheen. Use a 75/11 embroidery needle for 40 weight thread, store thread away from sunlight and dust, and change the needle if thread starts to fray or shred.

Embroidery thread looks like sewing thread but behaves differently. It is designed to lie smoothly in dense satin stitches and catch the light, and it runs at speed through a machine that changes direction constantly. Choosing the right fibre, weight and bobbin thread makes designs look better and cuts down on breaks and tension problems. This guide explains the main types, what the weight numbers mean and how to look after thread.

## The main types of embroidery thread

Each fibre has strengths. Most home embroiderers keep a polyester collection and add specialist threads as needed.

| Type | Look | Strength and care | Good for |
| --- | --- | --- | --- |
| Polyester | Bright sheen | Strong, colourfast, resists bleach | Clothing, towels, children's items, everyday use |
| Rayon | Soft, high sheen | Less strong than polyester, can fade with harsh washing | Decorative pieces, heirloom work |
| Cotton | Matt, natural | Softer, can lint more | Vintage looks, quilting designs |
| Metallic | Shiny, reflective | Delicate, needs slower speed and special needle | Accents and highlights |
| Bobbin thread | Fine, usually white or black | Lightweight | Underneath most designs |

Common machine embroidery threads (general guidance)

## What the weight number means

Thread weight is a size number where a higher number means a finer thread. **40 weight** is the standard for machine embroidery and most designs are digitised for it. **60 weight** is finer, used for small lettering and detailed designs that would look crowded in 40 weight. **30 weight** is heavier and gives bolder coverage.

Bobbin thread is usually **60 to 90 weight**, much finer than the top thread, so that it sits neatly on the back and adds little bulk. If you change top thread weight, the design density may need adjusting, so stick with 40 weight unless the design says otherwise.

## Matching needle to thread

Use an embroidery needle, which has a larger eye and a special scarf to protect the thread at speed. A **75/11** embroidery needle suits 40 weight thread on most fabrics; a **90/14** helps with thicker fabric or heavier thread. Metallic threads run better through a metallic or topstitch needle with a larger eye.

Change the needle every few designs, or sooner if thread shreds. Our [embroidery machine tension problems](https://stitchandhem.co.uk/blog/embroidery-machine-tension-problems) fix explains how a worn needle shows up in your stitching, and our [needle size guide](https://stitchandhem.co.uk/tools/needle-size-guide) covers sizes.

## Why thread frays, snaps or shreds

Fraying is usually mechanical rather than a thread fault. Check these in order.

- A worn, burred or too small needle
- Thread catching on a spool notch or cap, or twisting off a cone too fast
- Upper thread missing a guide, especially the take-up lever
- Dense designs stitched at high speed
- Old thread that has dried out or been stored in sunlight
- Metallic thread run at full speed without a suitable needle

## Storing thread and how long it lasts

Polyester thread keeps well for many years if stored properly. Rayon and cotton age faster and can become brittle. Keep thread out of direct sunlight, which fades colours and weakens fibres, and away from dust and damp. Closed boxes or drawers with racks work well.

If an old spool snaps easily when you pull a length between your hands, retire it for test stitching. Use a thread net on slippery spools so they do not pool, and place cones on a thread stand behind the machine where the manual recommends.

## Building a thread collection

Start with a polyester kit of common colours plus white and black bobbin thread, and add colours as projects need them. Some embroidery machine bundles include a thread kit; the Brother PE900 bundle listing, for example, includes 80 spools of polyester thread and pre-wound bobbins.

For machine choices, see [best embroidery machines for beginners](https://stitchandhem.co.uk/best/best-embroidery-machines-for-beginners), and for stabilisers that pair with your thread, read the [embroidery stabiliser guide](https://stitchandhem.co.uk/blog/embroidery-stabiliser-guide).

[See embroidery machines for beginners](https://stitchandhem.co.uk/best/best-embroidery-machines-for-beginners)

## Frequently asked questions

**Can I use normal sewing thread for machine embroidery?** It works, but all purpose thread is less shiny and thicker in dense satin areas. Embroidery thread gives a smoother finish.

**Is polyester or rayon embroidery thread better?** Polyester is stronger and more colourfast, so it suits clothes and items that are washed often. Rayon has a softer sheen for decorative work.

**What thread goes in the bobbin for embroidery?** A fine 60 to 90 weight bobbin thread, usually white or black, or pre-wound bobbins made for your machine.

**How long does machine embroidery thread last?** Polyester lasts many years when stored away from light and dust. Test old rayon and cotton spools for brittleness before use.

## Buying guides on this topic

- https://stitchandhem.co.uk/best/best-embroidery-machines-for-beginners
- https://stitchandhem.co.uk/best/best-sewing-and-embroidery-machines