Late model of the Scrivener Model 618 and 824 Surface Grinder
Housed in the base of the machine and coupled by just two connections to the hydraulic system, was the vane-pump-driven power unit, this being provided with pressure check points and running - to reduce aeration of the hydraulic fluid - at a relatively low pressure.
Automatically lubricated by an oil bath, the wheelhead assembly followed practice established over twenty years on Scrivener centreless grinders with the use of adjustable, plain, hard phosphorbronze bearings shrunk into the casting at -81° (though early models had what were described as lead-bronze bearings). The spindle, manufactured from a forging in nitralloy, was particularly stiff and designed to allow the fitting of oversize diameter wheels for use when dieset grinding. The patented Scrivener spindle thrust bearing was claimed to capable of easy and precise adjustment by unskilled labour - this presuming that all hammers were safely hidden away from them first….
Mounted at the foot of the vertical column, the main motor drove the spindle pulley directly through twin V-belts, their tension being set by the simple means of adjusting the motor platform's vertical position (when replacing such belts a matched pair are absolutely essential or, if not available, the use of T-link belts).
Entirely separate from the hydraulic circuit, the lubrication system provided a metered supply of oil to the table ways, this working continuously in either manual or power modes. Column and saddle-ways, column and saddle leadscrews and nuts were all oiled by a single-stroke, hand-operated pump - this reliability of this arrangement depending, of course, upon the inclination of the operator or efficiency of the service department.
All controls were grouped at the front of the machine, the table traverse control being coupled to a safety interlock that prevented power feed from being started when the table handwheel was engaged - the interlock also locking out engagement of the handwheel when the table was under power drive. Both the cross feed of the saddle and vertical movement of the wheel head could be directly adjusted by means of the handwheels to within 0.0001" (0.002 mm.) and 0.00025" (0.005 mm.) respectively while micrometer adjustments give further accuracy to within 0.0001 " (0.002 mm.).
One ingenious feature was a vertical fine-feed knob that incorporated a "click" plunger, this allowing the operator to set a cut of just 0.0001" (0.002 mm) by feel alone, his eyes thus remaining fixed upon the workpiece. Exclusive to Scrivener was the arrangement of the table speed control, this being set co-axially with the start-stop lever and giving independent control of the table traverse rate while permitting the machine to be instantly restarted at its original, pre-set speed.
All grinders were supplied with a complete electrical installation to a customer's voltage requirements, ready to run, with full overload and no-volt safety protection, waterproof push-buttons and the main isolating switch interlocked with the access door. To allow dust extraction and coolant equipment to be connected without having to modify the system, addition plugs and sockets were provided as standard.
Supplied with each new machine was a universal wheel guard suitable for wet or dry operation; one grinding wheel of standard diameter and width); an additional spare standard wheel; one mounted and one spare standard wheel-fitting adaptor and flange; a wheel balancing arbor; a diamond dressing holder (excluding the diamond); a set of four foundation bolts jacking screws and plates; two table T-bolts and nuts, spanners, keys, special tools, the initial hydraulic and spindle oils and a set of operating instructions.
Optional Extra Equipment consisted of: the previously mentioned two longer columns; an oversize grinding wheel for dieset grinding (10" diameter on the Model 618 and 14" on the 824); plain wet grinding equipment including a coolant tank, pump and motor, piping, fittings and splash guards; a coolant filtration system; coolant through-the-wheel; dust extraction; a wheelhead-mounted wheel-truing attachment for the 618; power rise and fall to the column on the 618; automatic down-feed; low voltage lighting; a more accurate thread-ground cross-feed leadscrew and split nut (in lieu of the standard cut thread screw and solid nut) for gap-gauge grinding; a variety of electric and non-electric magnetic chucks; standard machine and precision vices of various types; wheel-forming, sine and radius-dressing attachments; projectorscopes; "Profiloscope" form-grinding equipment and indexing centres..