tension block
Parts used to control thread tension.
tension disk 
Each of the parts between which the thread passes during threading.
tension dial 
Button that adjusts the tension based on the type of thread.
eyelet 
Hole through which the thread is passed.
tension guide 
Part used to direct the thread.
yarn rod 
Piece connected to the knitting machine; its function is to support the tension mechanism.
yarn clip 
Piece that holds the thread when it is not being used.
yarn tension unit 
Piece used to guide the thread toward the tension spring and keep it taut.
tension spring 
Spindle that maintains thread tension.