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Continued: Ruggedly constructed and accurately built the main spindle had a hardened nose (ground inside and out) a 1-inch bore and a 40 MMS taper - the assembly was guaranteed to run within 0.00015" of true. Speeds varied widely with age and model; early Standard versions, which all ran on taper-roller bearings, appear to have had four speeds driven from a 1 hp 3-phase motor (fitted with a gearbox on its output shaft to give a 300 rpm output,) of 100, 200, 600 and 1200 rpm. Later models were offered with five speeds and a choice either Timken taper-roller or ball bearings - the former with speeds of 100, 175, 365, 700 and 1350 rpm from a 1 hp motor, or 200, 350, 730, 1400 and 2700 rpm from a 1.5 hp motor with its gearbox modified to produce an output speed of 780 rpm. The high-speed ball-bearing model had the 1.5 hp motor as standard - but with a 900 rpm output - and spindle speeds of 250, 440, 910, 1750 and 3380 rpm; there was also the option of lifting the maximum speed to either 4000 or 5000 rpm by using special "pick-off" pulleys and fitting a stronger belt and pulley guard. It was also possible to change the speed range of an individual machine by fitting a different ratio gearbox to the motor - they were all interchangeable - but the makers cautioned against allowing the standard 5-step V pulley be run in excess of 1350 rpm and instead recommended the use of a safer two-part pulley. The absolute safe maximum speed for the taper-roller bearing models was set at 2750 rpm. At the opposite end of the scale, special pulley sets were available to bring the bottom speed down to 50 rpm - a modification which again required the use of a different belt and pulley guard. Two types of vertical head were available: the simpler of the two was mounted on the spindle head by a T-slotted ring adaptor and driven by a splined shaft inserted into the horizontal spindle taper. The unit was geared (up) to run at a ratio of 5 : 4 in comparison with the horizontal speeds, but was limited to a maximum of 2000 rpm; this meant taking care not to let the horizontal spindle speed exceed 1500 rpm - especially if the miller had been modified with a faster-output motor gearbox or high-speed pulley set when the marked speeds would not have been those achieved in practice. Driven from its own motor, and mounted on the end of the round overarm, the better of the two heads was similar in appearance and design to the those auxiliary types made by Halco, Tree and the Kearney & Trecker "Midgetmill" and "Speedmill" units. To see how these units were arranged, and the range of their capabilities, click here. The Nichols miller was supplied from the works complete with an electric motor and push-button starter, a machine light, an 8 gallon coolant tank (the pump and motor were extra), depth stop for the head, table stops, a hardened 1-inch diameter arbor with draw-in bolt, a belt guard and the necessary drive belts and wrenches. A typical Nichols weighted around 1175 lbs..
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