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Amongst the plethora of models listed by Portass from the 1930s to the 1950s the 3" x 16" Mk. 5 (not to be confused with the later PD5) must be amongst the rarest - only a handful having come to light in recent years. An entirely conventional machine, the lathe was also, surprisingly, badged as a "George Adams" - a brand more normally associated with high-class machine tools and with prices inflated to match. Weighing around 50 lbs, the Mk. 5 was entirely conventional with a simple, split-bronze bearing backgeared headstock (at a ratio of 1 : 6.75) and a spindle bored through 3/8" with a No. 1 Morse taper socket and a 3/4" 12 t.p.i BSF nose. Oddly, the headstock has been found both as a bolt-on unit and cast as-one with the flat-topped , V-edged, gap bed. Driven by changewheels 3/8" thick, with a 5/8" keyed bore and a sixth-of-an-inch circular pitch - about 18.812. DP - an odd figure presumably caused by the economical use of pre-war, non-standard gear cutters. The 24-inch long leadscrew was threaded for 11 inches of its length with a 9/16" 8 t.p.i. square thread and gripped by proper clasp nuts. Although a low-cost product, the lathe still had a compound slide assembly with its T-slotted, 5¼ x 2½" cross slide driven by a 5/16" 18 t.p.i. feed-crew. Although the top slide could be swivelled, it was locked down at the rear only - though as that on the far more common Drummond 3.5-inch lathe, as made from 1906 to 1941, used the same arrangement, it should not have caused any problems.
Offered in two forms, one as the simplest kind cast as one piece, the other with a separate bas that allowed it to be set-over for the turning of slight tapers. Pictures show the Portass-badged version with the superior tailstock, while the George Adams was fitted the lesser - though if this specification was set in stone is not known (nor, probably, did Mr. Portass…). Both versions held a 2-inch travel barrel (lock with a crude, direct-acting screw) with a 10 t.p.i. square thread that passed thorough the smooth-edged handwheel - an unfortunate oversight when it was likely to be gripped by oily hands.
Although most owners were happy to save the pennies and risk their fingers, Portass did offer a swing-open, cast-iron changewheel guard, though few can have been sold..
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The headstock, cast (in this example) as-one with the bed flat-topped, V-edged bed, carried simple split bronze headstock bearings. The backgear was a full-width, sliding type and, surprisingly for a cheap lathe of the period, a cast-iron cover was provided to guard the changewheels.
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Although not fitted to this example, the leadscrew handwheel grip on some models was in horn, something a little on the luxurious side for an early Portass. The rest of the machine was typical of the maker, with in-house manufactured handwheels and an inverted carriage rack that was prone to fill up with swarf and jam. The single-sided "thumb-action" compound slide rest handwheels were rather Drummond-like in appearance and, typical of an economy machine of the time, lacked any form of micrometer dial. The owner of this example has assembled the tailstock "back to front" on the bed, the clamp should be at the rear.
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