Built during the 1940s and 1950s to Schlesinger standards, the Nuttall 6.5" x 40" lathe was similar in specification to the contemporary Harrison L6 and built in both gap and straight-bed styles, the former intended for general-purpose duties and the latter, being more rigid, for heavy-duty work. It was offered complete with either a 2.75 h.p. 1430 r.p.m. motor built into the base and driving by four V-belts to a headstock input pulley (that, usefully, incorporated a combined single-disc clutch and brake of the maker's own design), or with just a single flat-belt pulley and no motor assembly - a money-saving consideration for those customers still surviving with a line-shaft-equipped workshop. Equipped with a gap bed and motor drive the lathe was catalogued as the Model "C", with a straight bed and motor driven as the "D", with gap bed and single pulley as the "E" and with a straight bed and single pulley as the "F".
Known to have made a relatively limited range of lathes - though all were proper industrial types - the 6.5-inch appears to have been the mainstay of the Company's smaller models (readers with Nuttall sales literature or a knowledge of the Company are invited to contact the writer) and was a well-built lathe constructed using high-quality materials.
Cast in a close-grained iron with a high nickel content, the flat and V-way bed was heavily ribbed by diagonal ways between its walls and featured a front way with the outer face made wider and set at a shallow angle (to slow wear) and the inside face made steeper and shorter to better absorb tool thrust. This feature, once popular amongst several makers, was to eventually to fall into disuse, the claimed improvements being unable to be confirmed in service conditions.
All-geared, the headstock had, as standard, twelve (rather slow) speeds in geometric progression from 16 to just 750 r.p.m. However, the makers did offer alternative speed ranges - obtained by the use of smaller or larger pulleys on the motor.
Made from heat-treated alloy steel, the 1.25-inch bore spindle ran in a pair of pre-loaded precision-class Timken taper-roller bearings behind the No. 3 Morse taper threaded nose - and in a single roller bearing at the other end. Made from chromium-nickel steel the headstock gears were heat-treated and lapped and the splined shafts carrying them supported in ball races. Splash lubrication was used (with a sight glass to check the level), the lowest gear in each train simply dipping into the oil and flinging it around. Speed changes were arranged in the Harrison/Colchester way using two levers on top of the headstock and a third, to select the high/low ranges, on the front face.
Drive to the Norton-type screwcutting and feeds gearbox was through an internally mounted tumble-reverse mechanism, the box providing 48 inch pitches from 6 to 330 t.p.i. and a range of coarse pitches from 1 to 56 t.p.i. - the latter by making use of an extra final reduction gear within the headstock instead of the usual Norton-type double gear arrangement on the end of the box itself. 32 metric pitches could also be generated with a set of changewheels obtainable at extra cost. Although the position of the sliding tumbler selector (along the open lower edge of the box) precluded the provision of an oil-bath, wicks, fed from a sight-glass-level-equipped reservoir, provided the bearings with a supply of clean oil. Sliding and surfacing feeds were driven by a separate keyed power-shaft below the leadscrew - with selection by a quadrant lever on the face of the double-walled apron and drive through a traditional worm-and-wheel arrangement. The latter system worked by lifting a worm, mounted inside a hinged housing with a trigger-equipped arm, into engagement with a wheel keyed to and sliding on the power shaft; the system providing an exceptionally easy-to-operate, snap-in-and-out control that did not load up, no matter how heavy the cut. Unfortunately, with an open base to the apron, the design did not allow the use of oil bath lubrication, and relied instead upon the whim of the operator to apply a pressure oil gun.
Rather Harrison-like (as fitted to early versions of the L5) the cross and top slides were fitted with micrometer dials engraved into the outer face of each handwheel, an arrangement that provided large-diameter, easily-read units at low cost - though unfortunately without any provision to zero them.
The number of accessories supplied with each new lathe was, for its time, generous and included fixed and travelling steadies, a 4-way toolpost, thread-dial indicator, faceplate, catch plate, a pair of Morse centres, three extra changewheels to extend the threading range, a chip tray and oil gun. Extras included 3 and 4-jaw chucks, chuck backplates, metric conversion changewheels, a taper-turning attachment, coolant and lighting equipment and an electrical reversing switch..
Parts for Nuttal lathes can be obtained from this source