Haas ST-20LY

The Haas ST-20LY puts a Y axis and BMT65 live tooling on the long ST-20 bed. It is an 8.3 in (210 mm) chuck lathe with 42.5 in (1,080 mm) of Z travel, ± 2 in (± 51 mm) of Y, and driven tools that run to 4,000 rpm, the same top speed as the 20 hp (14.9 kW) main spindle.

The point of the combination is milling along a shaft. Keyways, flats, cross holes and off-centre drilling can be cut anywhere on a long part without moving it to a mill. Y travel of 2 in (51 mm) either side of centre sets how wide a feature can be cut in a single pass; anything wider means re-indexing the part on the C axis. That axis does both jobs: Haas describes it as interpolated motion and positioning, with 0.01° positioning, up to 60 rpm and a 5 hp (3.7 kW) rating. A 13.9 in (353 mm) brake holds 250 ft-lbf (339 N·m) while a live tool cuts.

Adding the Y axis takes some envelope and some speed. Maximum turning diameter is 11.75 in (298 mm), where the two-axis ST-20L turns 13 in (330 mm). X and Y rapid at 472 ipm (12 m/min), half the 945 ipm (24 m/min) of Z. Thrust is 4,100 lbf (18,238 N) on X, 5,100 lbf (22,686 N) on Z and 2,300 lbf (10,231 N) on Y, so heavy drilling belongs on the spindle centreline along Z, not across the part.

At the headstock nothing is different from the two-axis machine: A2-6 nose, 3.5 in (88.9 mm) bore, 2.5 in (64 mm) of bar capacity and 150 ft-lbf (203 N·m) at 500 rpm. The table has no sub-spindle rows for this model, so second-side work is a separate operation. The machine weighs 12,360 lb (5,606 kg), and Haas lists a starting price of US$153,995.