Embroidery needles use a dual sizing system. The European metric size (e.g. 75, 80, 90) represents the needle shaft diameter in hundredths of a millimeter. The American size (e.g. 11, 12, 14) is a traditional numbering system. A higher number means a larger, thicker needle. Thicker needles push through heavy fabrics more easily but create larger holes. Finer needles (65/9, 70/10) are essential for delicate fabrics to avoid visible needle holes.

Thread weight (wt) is a measure of how many meters of thread equals a fixed weight. Counterintuitively, a higher number means a finer (thinner) thread. 40wt is the standard embroidery thread — it is the most widely used for commercial embroidery. 60wt is finer and produces less bulk, making it ideal for small text, fine detail, and lightweight fabrics. 60wt is also used for bobbin thread. Lower weights (30wt, 12wt) are thicker and used for bold, dimensional effects.

Bobbin thread connects with the top thread to form each stitch at the lockpoint inside the fabric. Using a fine bobbin thread (60wt or 90wt) reduces bulk underneath the embroidery, which is especially important on lightweight garments where a thick bobbin can cause the underside to feel stiff or show ridges through thin fabrics. Fine bobbin thread also reduces tension problems and is less likely to cause puckering, particularly on knits and delicate materials.

A ball point needle (SUK or SES designation) has a rounded tip that pushes the fabric threads aside rather than piercing them. This is critical for knit fabrics — the interlocked loops of a knit can be cut by a sharp needle, causing runs and holes in the garment. Always use a ball point needle on T-shirts, jersey, polo shirts, and any stretch fabric. On woven fabrics, a standard sharp needle is correct and will produce cleaner stitch holes.

Change your needle after every 8–10 hours of stitching time, or immediately if you experience thread breakage, skipped stitches, or popping sounds. A dull needle is the single most common cause of embroidery quality problems. Needles are inexpensive — changing them proactively is far less costly than fixing defective garments. For multi-head commercial machines, change all needles simultaneously to maintain consistent quality across heads.