A Precision Screw Machine is an automated turning machine that continuously creates a number of finished parts from bar stock. Bar stock advances through the spindle and is held by a collet. It is also commonly called a bar machine. In the hierarchy of manufacturing machines, the screw machine sits at the top when large product volumes are needed. An engine lathe sits at the bottom, taking the least amount of time to set up but the most amount of skilled labor and time to actually produce a part. A turret lathe has traditionally been one step above an engine lathe, needing greater set-up time but being able to produce a higher volume of product and usually requiring a lower-skilled operator once the set-up process is complete. Screw machines may require an extensive set-up, but once they are running, a single operator can monitor the operation of several machines.
Screw machines, being the class of automatic lathes for small- to medium-sized parts, are used in the high-volume manufacture of a vast variety of turned components. The name screw machine is somewhat of a misnomer, because screw machines spend much of their time making things that are not screws and that in many cases are not even threaded. However, the archetypal use for which screw machines were named was screw-making. Screw machines are either CAM or CNC driven or a combination. Multiple spindle machines are the most efficient since each spindle provides a station to sequentially add and progressively machine additional features on the part.
The biggest advantage to using screw machines is the reduction in the time required to machine a part and thus lowering the costs.