Chapter 4.3: Screw-Machine Products

THE PROCESS

The production of screw-machine products can use one of three basic machine types and many different combinations of metal-removing or -displacing tools. These tools operate on the internal and external surfaces of the workpiece in a predetermined, automatic sequence. The three basic machine types are Swiss, single-spindle, and multiple-spindle.

The Swiss-type machine incorporates five radially located tools with two to three end-working or axial tools (used for end drilling, tapping, or chamfering) as optional accessories. The incorporation of a sliding headstock permits the bar material, usually ground to 0.025 mm (0.001 in) or less, to be either advanced or retracted past the radial tools, which cut in a predetermined sequence.

The single-spindle machine can be equipped with from two to four radial tools and has a six- to eight-hole turret. The turret can contain tools that cut both internally and externally. The stock can be fed out more than once, depending on the work to be done. Figure 4.3.1 illustrates a typical single-spindle screw machine.

Figure 4.3.1: Typical single-spindle screw machine. ( Courtesy Wickman Corporation.)

The multiple-spindle machines are built with 4, 5, 6, or 8 spindles (one design contains 12). At each spindle there is a radial-tool slide and an axial-tool holder. All cross-slide tool holders and the end tool holders advance to the workpiece simultaneously to produce one completely machined component with each indexing of the spindle carrier.

A combination of any of some...