Of conventional design (though the top slide T-slot was in steel and bolted on) the compound slide rest registered against the front bed bevel and featured the usual long-travel (5.25") exposed-ways top slide. Both feed screws were of Acme form, 7/16" x 10 t.p.i. (or, optionally, 2 mm pitch) with that on the cross slide (with 5.25" of travel) completely enclosed, so protecting it from the wearing effects of swarf and dirt. Balanced handwheels were fitted, the retaining screws, as on most other Rivett lathes, passing down the stem of the ball-ended section. Micrometer dials (13/16" in diameter) also followed Rivett tradition in being clearly graduated in 0.001" intervals (or 0.02 mm) and fitted with very effective and sensitive knurled-edge locking screws (protruding through the ends of the balanced handwheels) that did not cause the setting to alter when tightened. Long bronze feed nuts were fitted, though (surprisingly) neither could be adjusted to remove backlash. The cross slide was equipped with a screw-adjustable rear stop (that could be transferred to the top slide) to aid threading and repetitive production work while the top slide, fitted with a full-circle graduated degree disc, could be rotated through 360°. An "American" toolpost was used, held in a T-Slot, and able to take an Armstrong or similar brands of toolholder.
Able to be set over for the turning of slight tapers, the No. 2 Morse taper tailstock mirrored the headstock in its use of clean, sharp-edged, very modern styling. With its outer end covered (an adaptation of the usual precision lathe design where this was left exposed) the hardened, ground and lapped 1.125-inch diameter spindle remained fully supported within the casting, no matter what its position. 3.5-inches of travel was provided, driven by Acme screw running through a bronze nut, with the casting cut away across its central section, to expose a finely engraved ruler scale 3.5-inches long graduated at intervals of 1/16". In addition - and fitted as standard - was a micrometer dial marked in divisions of 0.001"
Stand and Drive System
A choice of two stands was offered: a compact 45" x 24" all-welded, heavy steel-plate cabinet or a traditional open-type with a wooden top and cast-iron legs. The steel cabinet had an oil-pan top 53: x 21" x 1.75" deep (that drained into a 1.5 gallon sump) with two heavy-duty drawers both running on rollers and one having a collet-storage tray. Beneath the drawers was a locking tool and accessory cabinet and, to the left of that, a motor/countershaft compartment whose back wall was louvered for ventilation and removable to give access for maintenance. Electrical control gear was neatly contained within a separate chamber built into the left-hand face of the stand and fitted with an access door. Instead of being enclosed down to floor level, a space was left at the front, in the middle, sufficient for a seated operator to place his or her legs. As a final touch, at each end of the stand a pair of holes, fitted with blanking plates, was provided to take lifting hooks.
With its structure braced by steel tie rods, the open stand was topped by a large 60" x 26" by 2.25-inch thick 5-ply laminated wooden top with side and backboards. Also included were two locking wooden drawers, one fitted with a collet board. This stand was intended for laboratory and toolroom use - where it was necessary to mount the auxiliary motor unit and "overhead" to power high-speed grinding and milling spindles, or if space was needed for tools, small parts and sub-assembles to be laid out and a trail fit of components made.
Both stands used an identical drive system with a 2-speed 900/1800 r.p.m. motor, fitted with a 2-step V-pulley that drove to a matching pulley mounted on the rear of two shafts that extended from a simple clutch-gearbox unit bolted to the underside of the bench. Fitted to the output side of the rear shaft were high and low-speed pulleys that drove pulleys on the front shaft that were free to turn until locked by a sliding dog clutch.
Final drive to the spindle was by twin V-belts, assembled as a specially matched pair. In order to allow a quick release of belt tension for speed changes the motor was mounted on a hinged plate controlled by a lever hinged on a bracket bolted to the front face of the stand's lower shelf. By this (relatively complex) means the operator could juggle belt and clutch lever positions to give eight spindle speeds that spanned a very useful 150 to 3500 r.p.m. To promote smooth, vibration-free running, all rotating parts were dynamically balanced and ran in self-aligning ball races. Usefully, in addition to individual screw adjustment for each belt's tension, all could be changed without any dismantling being necessary.
With its use as a production lathe in mind, the electrical controls were more considerable more sophisticated than on the 715 - an automatic brake being provided that engaged whenever the control lever was moved to the central stop position. Combined with a pilot light (to indicate current on or off) the switch was moved to the right for high and low forward speeds and to the left for low and high reverse - a separate brake release switch being provided to allow the operator to turn the spindle by hand when the brake was on. In order to prevent burning of the switch, an electro-mechanical interlock prevented current from flowing until the finger contacts were in place. Sensibly, the makers made the switch handle of a decent size so that it could be gripped easily by an oily hand.
A wider range of accessories was offered for the 918 in comparison with the 715 and, in addition to the usual wide range of collets, collet closers and centres, the expected T and triangular rests in various sizes (hinged and plain) for hand work, drive dogs, fixed and travelling steadies, a faceplate with radial T-slots and a saw table, Rivett also offered a number of more advanced extras. Amongst these more expensive items were attachments for chase screwcutting, slotting, changewheel screwcutting using the top slide, ball-turning, indexing and internal and external grinding and honing units (available with drive from either an "overhead" or a self-contained motorised drive assembly). A lever-operated tailstock for sensitive drilling; a revolving-spindle tailstock for the drilling of especially fine holes and lapping work (this required an overhead drive to give speeds of 6000, 8000 and 10,000 r.p.m. in reverse direction to the lathe spindle).
An unusual design of milling attachment, almost certainly unique to Rivett, bolted to the bed in place of the compound slide rest. The unit consisted of consisted of a baseplate on top of which was a screw-controlled longitudinal slide able to be moved through 1.125" and swivelled through 360°. Mounted on the base and arranged vertically was a casting shaped to accept the ordinary compound slide rest (and indeed, other bed-mount fittings). This arrangement gave the assembly a wonderfully varied number of movements with its usefulness further increased by the availability of a large T-slotted table, an angle plate and machine vice.
One important accessory - and a unit common to this class of lathe - was the Universal Grinding Attachment, a device that allowed the lathe to be pressed into use as small cylindrical grinding or honing machine for internal, external, parallel and taper work. Supplied complete, ready for mounting on the lathe bed, the assembly comprised a base plate, fitted with a 5-inch travel slide that could be swivelled through 360°. On top of this was a bearing housing carrying a hardened, ground and lapped spindle (with 2.5-inch of hand-fed travel) that could be hinged clear of the work (for measurement and inspection) and then dropped back into position without loosing the previous setting. The spindle end was formed with a Pratt & Whitney No. 4 taper to mount grinding wheels and, using the 3-step pulley, could be made to run at 6000, 8000 and 10,000 r.p.m. in reverse direction to the lathe spindle. With lathe and grinding spindle both on top speed, an effective maximum r.p.m. of 35,000 r.p.m. could be obtained, a figure high enough for all but the very smallest of work.
Not listed, but almost certainly available if requested, was an attachments for the relief of cutters complete with its own drive pulley, gear set and a universally joined and splined shaft drive to the top slide.
*Other American makers from the 19th and 20th centuries included: Levin, Bottum, American Watch Tool Company, B.C.Ames, Bottum, Hjorth, Potter, Pratt & Whitney, Rivett, Wade, Waltham Machine Works, Wade, Pratt & Whitney, Rivett, Cataract, Hardinge, Elgin, Remington, Sloan & Chace, W.H.Nichols, Crystal Lake and (though now very rare) Bausch & Lomb, Frederick Pearce, Van Norman, Ballou & Whitcombe, Sawyer Watch Tool Co., Engineering Appliances, Fenn-Sadler, "Cosa Corporation of New York" and UND..