Haas ST-40SY

The Haas ST-40SY is a short-bed, large-diameter turn-mill lathe: 27.5 in (699 mm) of turning diameter, 28 in (711 mm) of turning length, a Y axis with ± 3 in (± 76 mm) of travel and BMT75 live tools that run to 4,000 rpm.

Consider the parts it is shaped for. A large flange needs its faces and bores turned, then a bolt circle drilled, perhaps tapped holes on the rim and a milled flat. On a two-axis lathe such as the ST-40S, which turns 30 in (762 mm) by 28 in (711 mm), those features wait for another machine. Here the C axis indexes or interpolates the part, with 0.01° positioning, up to 49 rpm and a 5 hp (3.7 kW) rating, and a 21.5 in (546 mm) brake holds it with 450 ft-lbf (610 N·m) while the live tool cuts.

The Y stroke covers pockets, slots and flats near the centreline. Anything further out on a wide part is reached by rotating C. Y thrust is 2,300 lbf (10,231 N), so heavy drilling is better done along Z, where 9,000 lbf (40,034 N) is available. X and Y rapid at 472 ipm (12 m/min) and Z at 710 ipm (18 m/min); the long-bed ST-40LY has the same X and Y rates but 320 ipm (8.1 m/min) on Z.

Turning capability comes from a 2-speed gearbox: 40 hp (29.8 kW), 1,400 ft-lbf (1,898 N·m) at 150 rpm and 2,400 rpm, with a 15 in (381 mm) chuck and 4 in (102 mm) of bar capacity. An XP option is listed at 55 hp (41 kW) and 2,100 ft-lbf (2,847 N·m) at 150 rpm. The 12-station turret indexes in 2 s, and the MT5 tailstock has 26 in (660 mm) of travel.

Haas lists a starting price of US$217,995. The machine is listed at 20,400 lb, or 22,141 lb (10,043 kg) in its export crate.