Johnford SL-50B

Big bore, low speed: the Johnford SL-50B carries a Ø132.5 mm (Ø5.2 in) spindle bore and an A2-11 nose on the shortest bed of the medium SL series. Bar capacity is Ø116 mm (Ø4.6 in), the chuck is 15 in, and maximum speed is 2,000 rpm.

The B spindle is the largest of the three offered on this bed, and it changes the machine's purpose. Material up to Ø116 mm passes through the spindle, so thick bar, tube and pipe can be fed from behind and worked at the end: threading, facing, boring, grooving. Couplings, pipe fittings, tool joints and large hydraulic components are the natural work. With a 15 in chuck in front of a swing over the cross slide of Ø450 mm (Ø17.7 in), turning large diameters over the slide is not what this configuration is for, and jaw clearance should be checked.

Power is 22 / 26 kW (29.5 / 34.9 hp) through a 2 step automatic transmission, the same motor as the SL-50A. The spindle bearing is Ø180 mm (Ø7.1 in), where the SL-50A has Ø160 mm (Ø6.3 in). 2,000 rpm on a bore this size is normal; it does mean small diameters are cut below their ideal surface speed.

Z travel is 650 mm (25.6 in), or 550 mm (21.7 in) with the Y-axis, and the machine weighs 7,500 kg (16,500 lb). Long tubes that stick out behind the spindle need support; the accessory list has a bar feeder interface but no rear steady, so that is a point to raise with the maker.