Manufactured by Costruzioni Meccaniche Tortona (C.M.T.) based at Corso Della Repubblica 74, 15057 Tortonia in Italy, a range of machines tools was offered including, during the 1970s, two heavily-built and useful general-purpose lathes the Ursus "52" and Ursus "105". The two lathes shared the same bed, complete carriage assembly, tailstock and screwcutting gearbox, the only difference being the bore of their headstock spindles - the former with 52 and the latter 105 mm - together with the necessary changes to the headstock casting, bearings and range of spindle speeds.
Each model was offered with between-centres capacities of 1000, 1500, 2000, 2500 and 3000 mm and centre heights of 200 mm (though for the Ursus 52 only), 225 and 250 mm. A detachable gap bed was standard and, with the gap piece removed, diameters of, respectively, 610, 660 and 710 mm could be swung with workpieces up to 180 mm in thickness mounted on a faceplate.
Mounted on separate headstock and tailstock plinths in cast iron, the 330 mm wide bed was heavily cross ribbed between its thick walls, induction hardened. and equipped with V and flat ways - thee V-way at the front having its outer surface made much wider and set at a shallower angle than the shorter, more upright inside face. Whether this design really did make a difference to longevity and accuracy - in comparison with a conventional symmetrical V - is open to discussion.
All headstock components, including the ball-bearing supported auxiliary gear shafts and gears, were made from case hardened and ground nickel-chrome steel with the spindle, running in ultra high-precision roller bearings made by Gamet in England, turned from a forging then hardened, stabilised and given a ground mirror finish. A choice of spindle end fittings was offered for the Ursus 52, the standard being a rather old-fashioned American Long-nose taper in an L1 size and the other an American Cam-Lock D1-6" and an American ASA A-6". On the Ursus 105, with its huge spindle bore, just one type of nose was supplied, a D1-8" Cam-Lock. Lubrication was by a pressure pump, the supply also being directed into the screwcutting and feeds' gearbox.
Drive came from a motor mounted inside the headstock end plinth, that on both sizes of the Ursus 105 being 10 h.p. and on the Ursus 52 being appropriate to the lathe's centre height: the smallest having 5 h.p., the middle sized model 7.5 h.p. and the largest 10 h.p. Power was transmitted by multiple V-belts and through a clutch unit co-axial with the input pulley; a powerful electromagnetic brake was fitted with control of start and stop by the usual third-rod system with levers (even on the models with shorter beds) mounted both on the right-hand face of the apron (and of course travelling with it) and just outboard of the screwcutting and feeds' gearbox. One experienced user reports that the control system was inaccurate, with the disengage point always some 5 to 6 mm further along the bed than anticipated; if this was a general fault, or specific to a particular machine, is not known.
Claiming that the screwcutting and feeds' gearbox and been the subject of very deep studies, all versions of both lathes were able to generate a range of English, Metric, Module and Diametral pitches without having to dismount of substitute any of the changewheels. Sealed, with changes made by dials and levers and not an open sliding tumbler, the box was proof against the ingress of dirt and swarf and used a separate set of gears for screwcutting and feeds - the latter by the usual slotted rod passing through a worm gear in the apron. Pitches available were Metric from 0.5 to 7 mm, English from 4 to 56 t.p.i., Module from 0.25 to 3.5 and Diametral from 8 to 112. Rates of longitudinal feed varied from 0.06 mm to 0.75 mm per revolution of the spindle with cross-feed rates set to be exactly twice as slow.
Heavily built, the carriage had a handwheel that could be disengaged during screwcutting, a saddle with adjustable gib strips on its underside and a completely enclosed apron with an oil pump automatically activated as the power feeds were engaged. Lubricant from the pump was distributed only to the apron, the bed and cross-slide ways requiring the turner to operator operate a plunger pump. A safety clutch was fitted to the powershaft drive that prevented overloading during either longitudinal or cross feeds, the same mechanism also serving to release the feed when adjustable stops were fitted to the bed or cross-slide ways.
Built as a full-length unit (and so better able to even out wear), the cross slide was fitted with two T-slots on its rear section for mounting a back toolpost and travelling steady. The cross-slide gib strip was tapered and, being fitted with adjuster screws at both ends, could be adjusted to give the slide exactly the required amount of smooth-running slack..
The writer seeks Ursus sales and technical literature and photographs of the lathes. If you can help with copies, loans ,etc. I will be delighted to hear from you.