Knitting machines differ in purpose, design, and type of knitting needles. All knitting machines may be classified according to the number of knitting needles per unit length of the needle cylinder. The most widely accepted system uses the English inch to measure the length of the needle cylinder. Machines produced in the USSR range in gauge from 3 to 36. The higher the gauge, the finer the fabric produced.
The principal working parts of a knitting machine are the looper, the yarn feed motion, and the take-up motion. The looper contains the needle cylinder with the needles, sinkers, a presser (for spring needles), yarn guides, and other elements. The sinkers, blades with complex shapes, bend the yarn into loops and move the yarn along the shaft of the needle (if the needles are stationary) or hold it (if the needles are moving); one sinker is usually positioned in each space between the needles. The presser, in the form of a wedge, plate, or disk, presses on the needle hook and prevents the loops from falling into the hook.
The knitting processes are automated by mechanisms that control the consistency of feed and yarn tension and the proper working order of the needles. They also rectify any defects that may appear, such as running loops. Electronic control devices have been developed for selecting or introducing the needles in knitting patterned.