What is the difference between regular thread and upholstery thread?
Upholstery Thread: Upholstery thread comes in a range of fabrics and weights and is used to upholster furniture. It's more durable and stronger than all-purpose thread. Cotton, nylon, polyester, and silk upholstery thread are all available. Silk thread, for example, is ideal for silk upholstery fabric.
Upholstery fabric requires special thread
For most upholstery jobs, all-purpose thread will do, although bonded nylon thread is recommended for added strength. The weather, UV, abrasion, and mildew resistance of the 3-ply 100 percent nylon thread makes it ideal for outdoor applications. It's best to use a size 18 needle, but if you're in a hurry, a size 16 needle will suffice.