Manufactured by Astorquiza Construcciones y Reparaciones Mecanicas, in Logrono, northern Spain (probably from the late 1940s until the mid 1950s) the Gurka "A-75" lathe was of conventional design and intended for use in general-engineering workshops and maintenance departments. With a 7-inch (175 mm) centre height, and able to take 30 inches (750 mm) between centres, the 235 mm wide and 1350 mm long bed used an unusual combination of V-ways: 90?for the carriage and (of a lower height) 70?for the tailstock. Machined from seasoned iron, the bed had its large feet formed as an integral part of the structure - adding to the weight and strength - yet the between-the-walls rectangular-form ribs appeared on the skimpy side.
Cut away to a point level with the spindle centre line, the headstock held a main shaft running in taper-roller bearings with (for the lathe's capacity) a rather tight 1-inch (24 mm) bore. Mounted very close to the back of the headstock, the countershaft assembly left no room for a conventional, rear-mounted backgear assembly; instead, as on early Clausing lathes, the gears were arranged below the spindle line with the headstock cover (again, like the Clausing) arranged to slacken and tighten the drive belt as it opened and closed. Although Astorquiza claimed a patent on this latter arrangement, it is unlikely to have succeeded. However, patented or not, the result was a machine of very compact dimensions from front to back, an achievement at odds with the normally space-hungry specification of all-V-belt drive from a rear-mounted countershaft. Fastened to an adjustable plate, pivoted on the back of the cast-iron stand, the 1.5 h.p. motor had a 2-step pulley driving up to a 4-step countershaft. Combined with strongly engineered (and quiet-running) helical-form backgears, this arrangement gave 16 speeds from either 30 to 830 r.p.m. or, alternatively, with larger pulleys on the motor, 60 to 1500 r.p.m. Electrical controls were limited to a remote isolator and a stop-start-reversing switch; however, presumably for countries with a more enlightened attitude to safety, a no-volt release push-button starter would have been added.
Passing through an ordinary, externally mounted tumble-reverse assembly, the drive from headstock spindle to screwcutting used changewheels that, without having to be replaced or changed around, allowed the Norton-type screwcutting and feeds gearbox to generate 20 English threads. A complete gear set - 30, 40, 50, 60, 60, 70, 75, 80, 90, 97, 100 and 120t together with a metric 127t translation wheel - were provided to extend the threading range and permit the development of 21 metric and 8 Mod pitches. As a handy touch, the top of the gearbox was fitted with a shallow tray to hold tools and other oddments. The leadscrew, 24 mm in diameter, was threaded 6 t.p.i. with a separate powershaft to provide sliding and surfacing feeds - the engagement of which was by a single lever that clicked the drive into and out of mesh.
Possibly adapted from a similar model of lower centre height, the cross and top slide castings appeared slightly out of proportion, probably having been thickened slightly to get the cutting tool up to height. The cross slide was unusually long, occupying most of its ways (probably because there was no option of a taper-turning attachment) but the top slide had only three gib-strip adjustment screw - insufficient to obtain a really good sliding fit under heavy loads. Micrometer dials, as might be expected on a lathe of this vintage, were woefully small, yet the balanced handwheel on the end of the cross-slide screw was fitted with a neat, rotating grip. A strong looking, 28-position, indexing 4-way toolpost, with automatic rotation by the top handle, was supplied as part of the standard equipment.
Unaccountably, the set-over tailstock had only a No. 2 Morse taper spindle that, combined with rather light castings, would have been unable to offer anything like the required drilling capacity for a lathe of this size and weight (725 kg). As a further aid to loss of efficiency, the makers included a self-hiding spanner to lock the unit to the bed.
If you have a Gurka lathe or machine tool of any type made by the Company, the writer would be interested to hear from you