The headstock spindle, running on 6" diameter Timken bearings and bored to pass clear a 2-inch diameter bar, was manufactured from a heat-treated nickel-chrome forging. It carried an ordinary threaded nose and was driven though its twelve (geometrically arranged) speeds by 5-V belts from a 1000 rpm 3-phase 3 h.p. motor mounted within the stand.

The oil-bath lubricated screwcutting gearbox, with its high-tensile steel gears and carbon steel shafts, held a four-speed gear change that was compounded with a traditional Norton design gear set to give 32 different threads from 2 to 28 tpi. With the substitution of an 84T changewheel threads from 4 to 56 tpi became available - and a metric screwcutting version of the machine was also available to special order. Both the leadscrew and power shaft could be reversed through the action of a "dog" clutch made from heat-treated nickel-chrome steel and operated by a lever on the outside of the gearbox. Sliding feeds varied from 0.007" to 0.1" and surfacing feeds from 0.005" to 0.77" per revolution of the spindle; with the 84T changewheel in place, these feed rates were halved. Instead of a sight-glass window, a dip stick was provided to check the oil level.

The distinctive, curved-edge apron was strongly built, of double-wall construction and carried a sturdy but easily-disengaged "drop-out" worm mechanism to drive the power sliding and surfacing feeds. The leadscrew clasp nuts were in cast iron and selection of power feeds by a single push-pull knob positioned on the face of the apron immediately below the cross-slide handle. The engagement of feeds was by Harrison's usual, convenient and safe flick-in-and-out lever the middle of the lower edge of the apron.