Other Bench Precision Lathes
From an unknown maker - though believed to be French - the AMSA lathe was a typical "Bench Precision" type intended to be used by a toolmaker engaged in simple but highly accurate work making one-off parts. This type of lathe was, typically, fitted with a headstock having a screw-operated draw-in collet attachment, a screw-action tailstock and a screw-feed compound slide. Although not fitted with screwcutting by a bed-mounted leadscrew, some makers did offer what was usually a beautifully made screwcutting and power feed attachment where a bracket, carrying changewheels, was bolted into the left-hand end of a T-slot that ran down the front face of the bed. A universally-joined shaft took the drive to the long-travel top slide.
Most "bench precision lathes" were also able to perform in two others ways, one as a "Repetition" or "Second-operation" lathe when fitted so that all movements - collet closer, cross slide, top slide and tailstock - were operated by quick action levers. The final type was as a production lathe, this too having time-saving lever-operation of every travel but also fitted with a bed-mounted 6-station capstan or "turret" head.
So fare two examples of the AMSA have been found, one set up as a toolmaker's lathe, the other as a second-operation machine - hence, the likelihood is that the makers would also have offered a bed-mounted capstan unit.
With a centre height estimated at 100 mm and a between centres capacity of perhaps 400 mm, the AMSA used a bed typical of its type with a T-slot running the length of the flat top face and bevelled faces at each side to accurately locate the headstock slide-rest assembly and tailstock. In this sense it was very similar to the well-known Schaublin 102, a Swiss-made lathe offered with a number of different headstocks, slide rests, tailstocks together with a very wide range of accessories.
The headstock appears to have held adjustable bronze bearings in which would have run a hardened and ground spindle. With bearing adjusters fitted to just their outside faces, it's likely that the front bearing would have been formed with two tapers, a long, shallow 3-degree and a short 45-degree taper (in the manner first adopted in 1865 by Stark in the USA) with, possibly, a plain parallel bearing at the other end.
Like most similar lathes, the compound slide rest assembly was located against the bed by a plate at the front slightly wider than the cross slide. Good-sized zeroing micrometer dials were fitted and the necessary long travel top slide, this having the usual two T-slots.
Drive came from a rear-mounted countershaft of the simple but efficient "overhung" type with a central post carrying the bearings and a pulley on each side - one driven by the motor the other driving to the headstock by means of a flat belt around 32 mm wide (on the lathe shown, the motor-drive is missing). This economic design of countershaft has been widely employed on lathes as diverse as the American Allen Electric and Swiss Agathon lathe - while the Simonet used a very compact unit that incorporated not only the electric motor but a 2-speed gearbox and take-off for an "overhead".
The AMSA join a short list of French made, plain-turning precision lathes that included the unusual S2F Cordima, the Crouzet, Jenny, Precis, a very early triangular-bed lathe, the Prudor, the S.O.M.B.V. and the "JCH", a make that came from Roanne, a small town to the northwest of Lyon (it's likely that they made a plain version of their unusual Type TG2).
Si un lecteur a une AMSA, l'écrivain serait intéressé de vous entendre ..