Haas ST-55

The Haas ST-55 is a large-bore lathe defined by one figure: a 12.5 in (318 mm) spindle bore. The spindle has A1-20 noses at the front and the rear, turns at up to 1,000 rpm and is rated 55 hp (41 kW) with 4,250 ft-lbf (5,762 N·m) of torque at 30 rpm. Maximum turning diameter is 25.5 in (648 mm) and maximum turning length is 80 in (2,032 mm).

Those figures describe a pipe and tube machine. A bore this size lets long stock pass through the headstock so that only the end being machined sits in the work area, and a nose at each end of the spindle allows workholding at the rear as well as the front to steady what hangs out behind. The low top speed is the trade for the bore. At 1,000 rpm, small diameters cannot reach high surface speeds, and a torque peak at 30 rpm shows the spindle is set up for large diameters and heavy threads.

Swing is 34.5 in (876 mm) over the front apron but 25.5 in (648 mm) over the cross slide and over the tailstock, and the last two set the working diameter. X travel is 17 in (432 mm). Rapids are 710 ipm (18 m/min) on X and 320 ipm (8.1 m/min) on Z, with 5,500 lbf (24,465 N) of X thrust and 9,000 lbf (40,034 N) of Z thrust. The table lists an MT6 tailstock with 76 in (1,930 mm) of travel and thrust between 1,000 lbf (4,448 N) and 4,500 lbf (20,017 N), and a 12-station BOT turret.

Against the ST-40L, which shares the 80 in (2,032 mm) turning length, the comparison is bore for diameter and speed: the ST-40L has a 4.62 in (117.3 mm) bore, 2,400 rpm and a 30 in (762 mm) maximum turning diameter.

Plan the installation early. The machine ships at 31,000 lb (14,062 kg) on a domestic pallet of 254 × 95 × 105 in (646 × 242 × 267 cm), and it draws 105 A at 220 VAC or 53 A at 440 VAC three-phase. Haas lists a starting price of US$355,995.