Specifications of the Myford Sigma Lathe

Ref: 947
Specifications of the Myford Sigma Lathe
The Super 7 Sigma is a 14 speed, belt driven, backgeared, screwcutting, bench mounted centre lathe, with a 3.1/2" centre height x 475mm (18.4/3") or 780mm (30.3/4") between centres, with the headstock spindle bored 26mm to clear 25.4mm (1") and incorporating a safe reversing feature. The spindle nose is precision bored and ground 4MT. Imperial model with 10 TPI cross slide and top slide feedscrews and nuts, inch graduations on the tailstock barrel and leadscrew handwheel; or Metric model with 2mm pitch cross slide and top slide feedscrews and nuts, metric graduations on the tailstock barrel and leadscrew handwheel. The lathe bed is cast in grade 240 iron and Induction Hardened Bedways are an optional extra on standard length beds only.

The lathe can be supplied as a changewheel model or fitted with a quick change screwcutting gearbox. On changewheel models, the 8 TPI leadscrew is driven by a standard train of changewheels which are set to give a longitudinal fine feed of 0.093mm (0.0037") per spindle revolution. Additional changewheels may be purchased to vary the speed rates and to facilitate the screwcutting. On quick change gearbox models, the gearbox, in conjunction with the 8 TPI leadscrew, gives 24 imperial/inch threads and 24 feeds, and a thread dial indicator is fitted to the apron. (for metric, BA, odd threads and pitches, the optional 1481/1 metric conversion set will be required).

The machine is fitted with a countershaft clutch unit. A plain taper front headstock bearing supports the spindle in radial loading, while a pair of angular contact ball races at the rear provide support for axial loads, the spindle nose is threaded M42.5 x 2mm pitch. The bullwheel has 60 teeth, 14 spindle speeds, ranging from 37 - 2105 rpm on 50Hz machines), which are achieved by a two-speed drive from motor to countershaft, a four-speed drive from countershaft to headstock spindle, and a backgear reduction.

The primary drive is fitted with a poly-V belt, and the secondary drive, a standard Vee belt. All drive guards are secured with 1/4 turn latches opened by a special square drive key.

The carriage feature a tee slotted cross slide, the top slide swivels 360 degrees, both cross slide and top slide feedscrews are fitted with adjustable micrometer dials.

The tailstock is a self-ejecting type, and the barrel feedscrew has a three start thread to give rapid movement. The barrel is precision bored 2 MT. The tailstock body can be set over on its base in either direction to turn long, shallow tapers.

The drive is motorised by a 0.55kW (3/4hp), 230 volts 50Hz, single phase, resilient mounted motor. A separate enclosure houses the push button on/off starter, with reversing switch, no-volt release, thermal overloaded protection to the motor, and turn-to release mushroom head stop button. Isolation and power inlet is via a CEE 17 plug with 3 metres of H07 insulated cable. A maximum of two additional control devices may be wired into this push button starter.

Where machines are required to operate on a 100volt 60Hz supply, the standard switch package is replaced by a rotary reversing switch with no volt release.

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