Star Micronics SW-20

The Star Micronics SW-20 is a Swiss-type lathe for Ø20 mm (25/32 in) bar whose usable part length depends on the guide bushing arrangement. Headstock stroke is 205 mm (8 in) as standard and 175 mm (6-57/64 in) with R.M.G.B. A part that falls between those two lengths settles the configuration before any other choice is made.

Among Star Micronics machines for this bar size the SW-20 is a heavy one. It is listed at 3,400 kg, against 2,750 kg for the SR-20J and 1,700 kg for the SB-20R Type G, both of which also take Ø20 mm (25/32 in) bar. Plan the floor and the rigging around that mass. The footprint row reads 2,588 × 1,300 × 1,765 mm.

Tooling is spread over three places. The front post holds 4 turning tools and a power-driven tool. The rear post holds 2 tools, a 4-spindle sleeve holder and a power-driven tool of its own, and the sleeve holder works in both directions with 4 front and 4 rear tools. For the sub spindle there is a back 8-spindle unit taking a maximum of 8 stationary tools and 6 power-driven tools. That split suits parts whose back end carries as much drilling and milling as the front.

Main and sub spindles are identical on paper: 10,000 rpm and 2.2 kW (continuous) / 3.7 kW (10min/25%ED) each. Equal spindles make it easier to balance a cycle between the two ends, but 2.2 kW continuous behind a 20 mm bar is a rating for free-cutting and moderate materials, not for deep roughing in hard alloys. The SW-12RII carries the same main spindle rating on Ø13 mm (33/64 in) bar and turns it at 15,000 rpm. The rapid traverse row names nine linear axes, X1 to X3, Y1 to Y3 and Z1 to Z3, in a faster and a slower group.