email: tony@lathes.co.uk
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Portass Mk. 5 (V) Lathe
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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 with prices 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 a T-slotted 5 x 2" cross slide driven by a 5/16" 18 t.p.i. screw,
Of the simplest kind, the tailstock was unable to be set-over for taper turning and 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..

Maker's illustration of the Mk. 5 as it appeared during 1939

Bed and headstock cast as-one and set up with the maker's changewheel guard and non-adjustable bench countershaft unit

Bench countershaft with round-rope drive from beneath

Alternative simple countershaft for wall or ceiling

A more expensive countershaft with a fast-and-loose pulley arrangement to give clutched drive

Wood turning

Using the Mk. V to the limit of its capacity

Front and rear toolposts and a tailstock drill being used to form, bore and part-off bar stock

Machining a 3/4" diameter 8. t.p.i. leadscrew with the help of  a travelling steady

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.

Although the leadscrew handwheel with its horn handle looks 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.


A Portass Mk. 5 badged as a George Adams - this example lacks the top slide

Ultra-rare changewheel guard - most owners preferred to save the pennies and risk their fingers

Rare Portass non-adjustable bench-mount countershaft unit


email: tony@lathes.co.uk
Home   Machine Tool Archive   Machine-tools Sale & Wanted
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Portass Mk. 5 (V) Lathe
Portass Home Page

Portass literature is available