email: tony@lathes.co.uk
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Harrison Vertical & Die-sinking Millers
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A Handbook & Parts List is available  for these machines




Competing in a keenly-fought section of the machine-tool market, the beautifully constructed Harrison vertical miller found far fewer takers than for the rugged and simple horizontal model favoured by educational and training establishments. The 8" x 30" table (760 x 205 mm), which had 15" (380 mm) of longitudinal movement, 6.5" (165 mm) in traverse and 14" (356 mm) vertically together with the knee assembly were identical to those fitted to the horizontal model. The table could be specified with either hand feed or an 8-speed power drive from a 1/8 hp motor-gearbox unit hung underneath its right-hand end with ratio changes by pick-off (demountable) gears. On power-feed models an automatic stop was fitted to the table while, at extra cost, an auto-cycle system was available with a rapid return of 280 inches (7 metres) per minute and control by 3 bed stops giving rapid-approach, slow traverse for cutting and high-speed return; push-button switches looked after the "Start", "Stop", "Inch Forward" and "Inch Reverse" control. The handwheel on new machines could be positioned at either end of the table - depending upon the customer's whim. Although the table and knee were from the horizontal model, the base, column, head and spindle drive were all unique - with a choice of two swivelling vertical heads offered: the simpler of the these was similar to that offered as an option for the horizontal version having a hardened nose, hardened and ground gears, Timken taper roller bearings, a 30 INT fitting and no quill feed - but without the step up gearing and angled drive both made unnecessary by a higher mounting and a dedicated, high-speed drive. The alternative head, a very rare fitting, enjoyed the benefit of a quill feed operated by both fine and rapid-action controls with a travel of 4 inches.
Held within the welded-steel cabinet base and suspended on a platform, the motor could be raised and lowered by a foot pedal to allow the 2-step Poly-Vee drive to be changed from one pulley to the other. From the motor the drive passed to a conventional gearbox, contained within the main column and controlled by two levers working in the usual Harrison way - each having a central neutral position that had to be selected before the other lever could be repositioned. 8 speeds were provided that could be set by the manufacture as either 119 to 3000 r.p.m. or 80 to 2000 r.p.m..

Harrison vertical with the standard, non-swivel  table

The rare quill-feed Harrison vertical head

Designed as a self-contained copy unit for work on small precision parts, the Harrison Die-sinking machine could also be pressed into service as a light-duty milling machine with a wide, if necessarily rather high, speed range.
The main body, knee, table and stand were the same as used on the standard horizontal model but, mounted in the dovetail on top of the column, was a sliding ram (moved by hand) with a high-speed head at the front and, at the rear, a 2-speed,  0.25/0.5 h.p., 3000/15000 r.p.m. motor. The drive from motor to head was by a single V belt running on 4-step pulleys to give speeds of 567, 828, 1150, 1680, 2310, 3360, 4670 and 6820 rpm. To sustain such revolutions the 30 International nose spindle was mounted in a pair of zero run out, pre-loaded angular-contact bearings at the nose and a roller bearing (to better withstand belt loads) at the pulley end . The head was fixed to the end of the ram and could not be rotated, nor did it have a quill. As an alternative, at extra cost, a very high-speed head was offered; this had a speed range from 15,000 to 45,000 rpm and a maximum collet capacity of 0.23".
The hydraulic copying equipment was similar to that used on Harrison lathes and built by the Yorkshire company of Hepworth; the table and knee assembly was servo controlled in the vertical plane whilst the tracer value unit was mounted on tubular slides with micrometer adjustment in three planes for ease of work setting. The valve spool was manufactured from a special alloy steel then stress relieved, heat treated and ground and slid in hardened and ground nitralloy bushes. The hydraulic cylinders that controlled the vertical movement of the knee and operation of the table were of large diameter (to give a positive resistance to cutting loads) and the unit was fitted with a mechanism to retract the knee rapidly to facilitate work changes.
The hydraulic accumulator unit was a stand-alone affair with built-in pump, pressure gauge, relief valve and motor whilst a thermostatically controlled heater and radiator maintained a constant oil temperature. The table feed-rate was infinitely variable with the large control box slung beneath the right-hand end of the table; adjustable stops limited the stroke and tripped the reversal of the table and, used in conjunction with the cross-feed pick, provided full 3-dimensional control.




email: tony@lathes.co.uk
Home   Machine Tool Archive   Machine-tools Sale & Wanted
Machine Tool Manuals   Catalogues   Belts   Books  Accessories

Harrison Vertical & Die-sinking Millers
Harrison Millers Home Page   Harrison Lathes

A Handbook & Parts List is available  for these machines