email: tony@lathes.co.uk
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Stima AMC Lathes - France

Stima "REP" and "RAC" Lathes


The Stima AMC company, with an office address in Paris and commercial address in the Rue de Selves, Brive (Corrèze) and at 2, Rue de la Cote, Nancy (Meurthe-et-Moselle), France, appear to have concentrated on heavy-duty screwcutting and production lathes of medium-size but considerable weight and great strength - a notable feature of all their machines being the casting of the bed and stand as a single structure in Meehanite cast iron. They were all constructed to the French Standard for precision lathes - Salmon Standards Table 111B. In the 1950s, as the contribution that automatic systems could make to output and quality became more clearly recognised, the company offered a selection of lathes interesting in that all their operations were achieved without the aid of plug-board or computer technology and relied entirely upon ingenious interfaces between mechanical, hydraulic and electrical systems. By the early 1960s the AMC range consisted of the Models 190, 240, 560, "REP" and "RAC" - typical of these beingthe "560" screwcutting lathe - a machine that also reflected the general layout and construction of the versions adapted to automatic controls. Known later as the "Élan" it was a model available with various specifications during its production run including both 9.5-inch (240mm) and 7.5-inch (188-mm) centre heights and with capacities between centres of 31.5, 49 or 63 inches (800, 1250 and 1600 mm.)
The base of the "560" had 6 5/8-inch diameter bolt holes and 6 levelling screws with a large chip box provided in the central section that could be slid out from either the front or rear; beneath this a compartmentalised coolant settling tank was fitted, with a pump that could be easily withdrawn for cleaning or maintenance. At 15-inches across the V and flat-ways bed was exceptionally wide and cross braced with deep, diagonal ribs; the customer was given the choice of either hardened slideways or, at extra cost, with hard-chrome plating - a finish  resistant both to wear and chemical attack by combinations of coolant and the swarf from exotic materials. Although no gap-bed version was offered (it would have compromised rigidity), at the headstock end the inner ways (those carrying the tailstock) were cut short in relation to the outer by some 11.75-inches, so allowing slightly larger-than-normal diameters to be turned in the resulting space. The back of the bed was equipped with a socket and bracket to fit an optional-extra lighting arm and T-slots were provided to mount either taper-turning or hydraulic copying attachments.
Continued below:

Stima AMC Model Élan/500

Continued:
The No. 5 Morse taper headstock spindle, bored to clear a 1.57-inch diameter bar and with an A1-6" size American nose, was in a nickel-chrome steel, hardened, rectified and ground. At the front it ran in a pair of pre-set opposed conical roller bearings of the "Machine -tool Type 0" - a specification that guaranteed radial play of less than 0.000016 inches. The spindle assembly was dynamically balanced and the whole assembly lubricated by a pressure pump with oil throwers to limit leakage.
The drive system and its operating controls, as befitted a machine intended for arduous, long-term duty, were well thought out and solidly engineered. Electrical push-button contactors ran at 24 volts for safety and all circuits were protected by a combination of thermal relays and fuses. The motor,  6 h.p. as standard but also optionally of 4 or 8 h.p., was mounted in the cabinet base and flanged directly to an 11-speed (Raynard range) gearbox with a built-in Type MG3 SIGMA double clutch unit. Running in the same splash oil-bath as the gearbox, the clutch was arranged to give instantaneous forward or reverse at any speed whilst a mechanical brake, automatically synchronised with the clutch control, brought the spindle to a halt at the moment of declutching. This feature not only allowed the time between work-piece changes to be kept to a minimum but also encouraged the operator to select the right speed for the job - the time wasted in stopping and starting the spindle being negligible. The clutch and brake assembly was operated by a lever pivoting from (and moving with) the right hand face of the apron and connected to a long control rod below and parallel to the leadscrew. However, even on the longest-bed versions, the control lever was not (probably because the carriage ran right up to the outer face of the screwcutting gearbox), duplicated at the headstock end as it was on most other makes. If the customer so desired, the automatic application of the brake could be disconnected and a foot-operated brake-bar supplied instead. Drive to the spindle was by 7 V-belts, the pulley at the spindle end being independently mounted and so allowing the belts to be changed without the need for dismantling. A long boss, extending from the side of the gearbox and passing through the front of the stand, ended in two conveniently positioned (if rather long) gate-change levers by which means the spindle speeds were changed. A useful and well-spaced 22 speeds were provided: 11 from the gearbox and the others by engaging a headstock-mounted backgear. For the 9.5-inch lathe the full speed range was, in backgear: 31, 40, 50, 63, 80, 100, 125, 155, 190, 250 and 310 r.p.m. and, in direct drive: 250, 310, 390, 500, 630, 780, 990, 1250, 1520, 1530 1960 and 2500 r.p.m. Alternatively, a slower range of speeds could be specified: in backgear: 20, 25, 31, 40, 50, 63, 80, 100, 125, 157 and 200 r.p.m. and in direct drive: 157, 200, 255, 320, 400, 500, 630, 800, 990, 1260 and 1600 r.p.m.
On the 7.5-inch model the available speeds were adjusted slightly to give a standard range the same as the slower alternative on the 9-inch (20 to 1600 r.p.m.) or, by paying a supplement, to be the same as that lathe's standard set (31 to 2500 r.p.m.).
Continued below:

Stima AMC Model Élan/500

Continued:
Although of identical design and external appearance the totally enclosed, oil-bath screwcutting and feeds gearbox was of different specification for the 7.5 and 9.5-inch lathes. Containing hardened and ground gears in a high-quality steel on the 7.5-inch the box was able (without disturbing the changewheels) to generate English threads from 1.28 to 244 t.p.i and metric from 0.08 to 14 mm pitch. Longitudinal feed rates varied from 0.00118 to 0.0777-inch per revolution of the spindle with the surfacing rate set to give a feed half as slow. On the 9.5-inchj the box was set to generate English pitches from 2.57 to 56 t.p.i. and metric from 0.32 to 14 mm - again without having to alter the position of or change any gears. As an option the carriage could be fitted with a drop-in device that allowed the pitch to be picked up again after the clasp nuts had been opened when screwcutting. The leadscrew was either of 4 t.p.i or of 6-mm pitch Acme thread, 1.57-inches in diameter and protected by a simple shear pin; both it and the shaft to drive the power feeds could be instantly reversed by a small lever on the face of the box.
The carriage was enormously strong with both power sliding and surfacing feeds selected and engaged by a single apron-mounted lever operating a clutched drive. Whilst the power-feed shaft passed through the usual sort of apron-mounted worm gear this was supported not in plain bearings but a conical roller assembly running, together with its mating wheel, in an oil bath. The power shaft was also fitted with a precision clutch that acted both to protect the drive in case of an overload or (if ordered as an extra) in combination with a 6-position drum to either automatically disengage the drive or act as a solid carriage stop.  The power cross feed, was also (for some, if not all variants of the lathe) fitted with an automatic knock-off that acted in both directions or, alternatively, when locked, as a positive stop. The carriage hand-traverse wheel, mounted either on the left for the American market or on the right for other destinations, was fitted with a large-diameter, vernier-scale micrometer dial. In keeping with the rugged build and long-life expectancy of the lathe the carriage was fitted with a centralised lubrication system, fed by a "Mecafluide" pump mounted under the saddle bridge, to provide an oil supply to the bed and cross slide ways. As a further refinement the cross-feed screw and its special bi-metallic nut (a steel body lined with anti-friction material) were run in an oil bath inside an oil-tight case.
The wide cross slide was in steel and machined at the rear with side dovetails to mount a range of optional tool-holders.  The top slide could be rotated through 360-degrees and was fitted as standard with a special 4-way toolpost that guaranteed accurate re-engagement in 4 positions. Both top and cross slides were adjusted by tapered gib strips.
The tailstock was fitted with a 2.75-inch diameter, 5-Morse taper barrel, graduated with both inch and metric ruler markings and operated by a large handwheel with internal finger grips and a vernier-equipped graduated micrometer collar reading to 0.001". For repetitive drilling operations a quick-action, 3-spoke capstan assembly could be ordered to replace the handwheel assembly. The tailstock was locked to the bed by a handle protruding from its right-hand end face - with an additional bolt available for heavy-duty work - and topped by a removable plastic tray for the storage of delicate measuring instruments.
The 7.5-inch lathes weighed 3360, 3800 and 4556 lbs for the 800, 1250 and 1600 mm between-centres models respectively and 3500, 3944 and 4667 lbs for the same lathes with a 9.5-inch centre height. Respective overall lengths for both models were: 6' 10", 8' 3" and 9' 2" (2070, 2500 and 2800 mm)..

Running in the same splash oil bath as the gearbox, the clutch was arranged to give instantaneous forward or reverse at any speed whilst a mechanical brake, automatically synchronised with the clutch control, brought the spindle to a halt at the moment of declutching.

The main drive motor,  6 h.p. as standard but also optionally of 4 or 8 h.p., was mounted in the cabinet base and flanged directly to an 11-speed (Raynard range) gearbox with a built-in Type MG3 SIGMA double clutch unit. 


Stima "REP" and "RAC" Lathes

Stima AMC Lathes - France
email: tony@lathes.co.uk
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