1.2.1 Machine tools
• There are two tool feed mechanism on most lathes. These cause the cutting tool to move when engaged.
- The larger screw (the lead screw) will cause the lathe cutter to advance quickly. This is used for cutting screws, and for moving the tool quickly. Typical feed rates range from about 0.05” to 0.5” per revolution.
- The small screw (the feed rod) will move the cutter slowly forward. This is largely used when doing rough cuts, or finishing operations. Typical feeds with this screw range from 0.001” to 0.010” per revolution.
• On a lathe the axial distance of the tool on the part is set by the carriage. A compound rest is used on a lathe that allows the radial tool position and orientation or the cutting edges.
• Work is held in the lathe with a number of methods.
- 3 jaw self centering chuck
- 4 jaw independently adjusted chuck
- Between centres
- Face Plates
- Mandrels
- Collets
- Soft Jaws
1.2.1.1 - Production Machines
• In production there are a variety of cutting machines used to increase throughput by automatically feeding stock (through the headstock).
• Other types of turning centers provide multiple operations on a single machine,
- Multispindle - Multiple spindles in a single machine allows parallel operations in a single lathe. Between each operation the spindles are advanced to the next operations.
- Rotary Transfer - Large machines where parts are moved to different stations, typically over ten stations. These may have other tools such as drills mounted.
- CNC machines - These computer controlled machines are typically flexible, but a bit slower. Flexibility is enhanced by a wider variety of operations and multiple tools in the same machine.
- Cam - For high production rates, cams can be made to drive the cutting heads. Their geometry will move the tool in complex patterns.
