II il I T I I i l b The small lever (G) is used in conjunction with gear- box controls for reversing the direction of feed. THE SPINDLE AND HEADSTOCK GEARING MUST ALWAYS BE STOPPED BEFORE MOVING ANY OF THE CHANGE LEVERS. A shear pin safety device is fitted as a measure to protect against overload when screwcutting. A broken shear pin can be replaced easily by removing the top gear in the train, then the splined sleeve which carries the gear. The broken portion of pin may then be tapped out of the sleeve, from the side opposite to the splines.
To remove the other broken portion, the shaft should be rotated until the pin hole is opposite the slot in the housing and swing frame then the broken pin may be knocked straight through and will drop out through the slot. A new pin can then be inserted and the top gear and sleeve re-assembled. In case of difficulty in obtaining new shear pins they can be manufactured from $ in. mild steel rod to British Standard ENIA (shear strength 20 tons per sq, in.) No other material should be used. PRESS C0.mnMAZoo.MtCH. U.S.A. DO I{OT CHAI{GE SPEED WHITE RUI{NII{G GEARBOX The standard gearbox covers a range of 45 feeds and threads (including 11| and 23 t,p.i.) but does not provide metric threads.
The full range of feeds and threads available are shown in the reproduction of the machine data plates. Control of the gearbox is by means of four levers (1,2,3 and 4 in the illustration) and the tumbler shaft (5). The tumbler shaft is provided with a spring- loaded plunger which engages with holes in the front of the gearbox cover to provide positive positioning and locking. The two selector levers (1) and (2) at the left-hand end of the gearbox each have two positions (A or B) and (C or D) and by manipulating these two levers in conjunction with the tumbler arm a range of 36 feeds and threads can be obtained.
The remaining 9 feeds and threads of the total 45 are obtainable by substituting a 36T change gear for the 18T gear on the top driver position and re-meshing the train. This 36T change gear is supplied stowed alongside the 42T change gear on the gearbox driving shaft. SPINDLE AND HEADSTOCK GEARING MUST BE STOPPED BEFORE ANY OF THE LEVERS CON- TROLLING THE GEARBOX ARE MOVED. A third lever (3) disengages the leadscrew when this is not actually required for screwcutting. A lever (4) situated high on the front of the headstock controls direction of the feeds, reVersing them as required.
; r n I THE COTCHESTER TAIHE CO.tID.EIIGIA]ID SWING FRAME The drive from headstock to gearbox is transmitted through the train of gears on the end of the headstock, enclosed by the end cover. The gears are fitted to a swing {rame assembly which is readily adjustable to accommodate the full range of change gears available for each particular machine (see also Section GEARBOX). At each of the gear spindles a knurled handnut is fitted to enable gear wheels to be rapidly interchanged when required. Be sure to tighten the handnuts after fitting each gear wheel.
l-, \ t NOTE:-The leadscrew should never be allowed to revolve except when screwcutting; it should be cleanedandliohtlvoiledeachtime before use,