Founded by Mr Zachry Brierley and located in Llandudno Junction, North Wales, the Brierley Company launched its first machine in 1962. The basis of the initial design was to remain unchanged but made, over the years, in several different models including the ZB, ZB10, ZB11, ZB20, ZB21, ZB25, ZB32, ZB50, ZB60, ZB80, ZB80SA and TC32 the latter consisting of a main spindle and chuck on its swivel housing adapted to fit on the table of a tool and cutter grinder. A simple, less expensive self-contained unit was also offered, the "Cadet". The machine model number indicated its maximum holding capacity in mm. A second generation of models was also manufactured, this set including the Types ZB32/2, ZB50/2 and ZB80SA (semi-automatic) and then, moving into the computer age, what was claimed to be the world's first micro-processor-controlled drill grinders, the ZNC51 and ZNC32/51. These pages cover the original, traditional, UK-made types - the Brierley name now being owned by Chester Machine tools - who have similar and CNC models made for them in China.
Designed for ease of use, even by unskilled labour, a Brierley can grind a wide range of sizes and drill form, the drill to be ground being held in a precision, 6-jaw chuck, positioned with the aid of a setting piece and the chuck rotated so grinding both lips in one operation. The drill is advanced by a screw-feed, or a lever, the latter also used to quickly withdraw the drill so the next can be loaded more quickly.
The work head (the assembly holding the drill) can be rotated to produce the point angle needed - between 40 and 180 degrees - though as the standard angle is 118 degrees, this alteration of setting is hardly ever required.
The clearance angle - or "back off" - can be adjusted by a control arm that automatically varies the effect of the setting cam - the variation being unaffected no matter what cam is in use.
Although essentially simple in operation, to get the best from a Brierley, reference to the various instruction books is essential, as is some time spent practising the various operations and carefully checking the results afterwards.
Intended for heavy-duty use, by the time the Brierley Mk.4 model was in production, the workhead contained fourteen anti-friction bearings. Needle-roller bearings and thrust races were fitted to the cam and layshafts with the main spindle, upon which the chuck ran, having large diameter radial thrust races at each end and rotating in a special "Rotolin" bearing. The latter unit allowed a maximum deflection of just 0.0002" - the makers claiming that, although sealed against the ingress of grinding dust, the bearing could still function even in dirty conditions and without the need for frequent lubrication.
Although a standard machine could do most jobs - including "Truax" spiral-point, Plastipoint (drill for plastics) subland and prismatic four-facet point grinding to suit the needs of CNC machines - some accessories were available included point-thinning, point-splitting and radial-relief attachments and a grinding wheel balancing stand..