Many household sewing machines and computer embroidery machines use flat pins. (The handle of the needle is round, but the side is flat), while the commercial machines use round pins.

When embroidering, it should change a new needle every 8 hours. A blunt or hairy needle will hook the embroidery or crease the embroidery, so if you have a needle problem, try replacing a needle. Although it is not always the best choice to avoid wear and tear, a small needle can cause tension problems. The thick embroidered needle will leave an ugly pinhole in the fabric, or even damage the fabric, creating a gap between adjacent embroidery areas. 

To test whether the embroidery you use is too much tension for the thread, you can cut an embroidery thread about 12 inches and put it in the embroidery needle. Tighten the line vertically and then, let the embroidering needle slide down from the top. The needle should slip to the bottom, and if it doesn't slip, you need to change a needle with a large needle.

Choose the appropriate thick embroidery needles based on  the weight and type of the fabric you will use and the thickness and type of embroidery thread. Thicker and more densely woven fabrics should be used with a thicker embroidery needle, and vice versa.

The most commonly used embroider needle specification on the computer embroidery machine (Using European and American standards) is 65/9, 70/10, 75/11, 80/12, 90/14. Compared with sewing machine needle, The embroider needle used in the computer embroidery machine has a larger and smooth needle eye, and there is a slot on the handle to prevent the embroidery thread and/break line. There are many kinds of embroidery needle - pointed, clap-head (cutter), spherical head and alloy type:

A pointed needle is suitable for most woven fabrics. A pointed needle is woven into the fabric, and a small force is needed to pull the thread through the fabric and pull it out of the fabric.

The ball - head embroidery needles are used to embroider the knitted fabric and other stretchy fabrics. It is important to avoid cutting the yarn when it is required to pass through the fabric. A spherical head stitch will allow the needle to slide in the fabric of the cloth to avoid cutting the cloth.

The clap-head embroidery needle is used to embroider leather, synthetic leather and other thick, especially dense materials. The needles are used for non-woven fabrics that only have a small crack in the fabric instead of a hole. Using the wrong needle will make embroidery out of the leather.

Fortunately, embroider needle manufacturers also designed wonderful embroidery needles for special computer embroidery threads, such as gold and silver lines, bright lines and other unusual lines. Special embroidering needle (such as Sullivan's Metafil，Madeira's Metallic，Schmetz Metallica) has a large needle eye and a deep groove on the handle, which makes threading easier.

It is a good idea to make sure your embroidery in good state before embroidering your product.