Haas ST-55Y

The Haas ST-55Y is a long-bed, big-bore turn-mill lathe: 80 in (2,032 mm) of Z travel and turning length behind a 12.5 in (318 mm) spindle bore, with a Y axis, a C axis and BMT75 live tooling. It turns up to 27.5 in (699 mm) in diameter inside a 35.5 in (902 mm) swing.

Its axis layout matches the ST-40LY figure for figure: 20 in (508 mm) of X, ± 3 in (± 76 mm) of Y, 80 in of Z, rapids of 472 ipm (12 m/min) on X and Y and 320 ipm (8.1 m/min) on Z, and live tools at 4,000 rpm. The difference is the spindle. The ST-40LY has an A2-8 nose, a 4.62 in (117.3 mm) bore, 40 hp (29.8 kW), 1,400 ft-lbf (1,898 N·m) at 150 rpm and 2,400 rpm. The ST-55Y has an A1-20 nose front and rear, a 12.5 in bore, 55 hp (41 kW) through a 2-speed gearbox, 4,250 ft-lbf (5,762 N·m) at 30 rpm and 1,000 rpm.

A long bed changes how the machine is used. The MT6 tailstock travels 84.5 in (2,146 mm), a little more than the Z stroke, with thrust from 200 lbf (890 N) to 3,000 lbf (13,345 N), so a shaft or casing can be supported wherever its end falls along the bed. Z thrust is 9,000 lbf (40,034 N). The Z rapid is the slowest of the three axes, which matters little when the cutting passes themselves are long.

On the milling side the C axis is rated 5 hp (3.7 kW), runs to 49 rpm and positions to 0.01°, and its brake holds 450 ft-lbf (610 N·m). Y thrust is 2,300 lbf (10,231 N). Ports, slots and flats can be placed anywhere along a long tube, provided they sit within the Y stroke of the centreline or can be reached by rotating C.

Before ordering, confirm the workholding, since the table gives no chuck size or bar capacity, and the supply: 105 A at 220 VAC three-phase or 53 A at 440 VAC. Haas's starting price is US$419,995.