Although most Triumphs, especially those destined for the home market, were fitted with a bed having a detachable gap, T-slotted apron wings and an oil-bath screwcutting gearbox that was able, at the flick of a lever, to cut 36 English pitches from 4 to 60 t.p.i. and 11 metric pitches from 0.5 to 6 mm, another, cheaper model, the "Dominion 15-inch" was also manufactured. This lathe lacked the T-slotted wings, the gap bed and was fitted with English screwcutting only, although with two additional pitches of 11.5 and 23 t.p.i.. On both lathes 36 sliding and feeds were available from 0.0033" to 0.048" per revolution of the spindle with the same number of surfacing feeds but at exactly half the rate (0.0015" to 0.024"). A set of extra changewheels was available to extend this range in both directions, though in some cases, when large changewheels were fitted, the otherwise inconvenient stud-mounted cast-aluminum gear and belt-drive cover had to be left off to avoid fouling the gears. Later models had an improved gearbox with 45 English threads and feeds and 12 metric pitches; the English range stretched from 120 t.p.i. to 4 t.p.i. and the metric from 0,25mm to 6mm pitch with the sliding feeds varying from 0.0017" to 0.48" per revolution of the spindle and, as before, the surfacing speeds set to one-half of those values.

Gap-bed Triumph with T-slotted saddle wings, the apron traverse handwheel on the right and leadscrew clap nut handle on the left.   

The apron was double walled but open at the bottom, so precluding any chance of the gears being run in oil; the power feed controls followed standard Colchester practice of the day being concentrated into a single lever that slid along the lower edge of the apron and was lifted into one of two slots to engage either power sliding or surfacing. Lifting the lever automatically locked the engagement whilst stopping the feed merely required the lever to be pressed downwards; unfortunately, the heavier the load on the feed the greater the effort required to disengage it, but at least it was a positive action and did not require a knob to be unscrewed in order to release a clutch.

Interior of the apron. The long pointed arm laying against the inner wall was part of the interlock mechanism that prevented the simultaneous engagement of power feeds and screwcutting.

Although not fitted to the very first machines, most of the first-model Triumphs had a simple but ingeniously-contrived spring-loaded ball-bearing "clutch" built into the junction of the powershaft rod with its gearbox connection..