GB1280087A - Special purpose machine tool - Google Patents

Abstract

1280087 Milling helical grooves CREED & CO Ltd 26 Nov 1970 56196/70 Heading B3K A machine for milling helical grooves in a cylindrical workpiece comprises two milling cutter assemblies movable in opposite directions along a left and right handed lead screw 9, a drive shaft 4 driving each of the cutters 32 continuously through a gear train 25, 24, 27, 30, a work collet 19 driven from the lead screw by gearing 14, 22, 21, a work centre 17, and a detent and trip arrangement which allows pivoting of a support carrying the cutter assemblies about the axis of shaft 4, so that half nuts are adapted to engage the screw thread on the lead screw, and the cutters are brought into engagement with the workpiece held between the collet and centre so that machining can be carried out. The machine has a U-sectioned frame, 2, 3, Figs. 4-6 which supports the cutter drive shaft, lead screw 9, collet 19, and centre 17. Shafts 9 and 4 are belt driven by a motor, through a reduction gear and clutch, shaft 9 is driven at a much slower speed than shaft 4, and the collet is driven at a lower speed than the lead screw. Each cutter assembly comprises a cutter frame 23, Figs. 1, 8, carrying the gears 25, 24, 27, a half nut 29 for engagement with the lead screw, a skewed cutter spindle assembly, Fig. 9, whose gear wheel 30 meshes with gear wheel 27. A further half nut 34 which matches with half nut 29 is carried by a swinging lever 33 having a support wheel 35 which rolls along a rail 36. Each frame is slidably mounted on rods 38, 39 fixed to cross-pieces (40), (41), Figs. 2 and 3 (not shown), the pieces being pivotable about shaft 4. Rail 36, Figs. 4 and 8, is pivotal about pivots 56, 57, and is connected to frames 23 by levers 55, 59 and 56, 60. Hooks 61, 62, Fig. 7, depend from the cross-piece and engage spring loaded detents 63, 64. A transparent rigid guard 65 is pivoted on arms 66, 67 and when downward pressure is applied to the guard, frames 23 are pivoted about shaft 4 until they are latched. A workpiece is fed through the collet and clamped, the guard is pressed further down so as to tilt frame 23, the lead screw is engaged by the half nut, and the rotating cutters are fed along the workpiece so as to cut opposite hand helical grooves. When the machining is complete, detents 63, 64, Fig. 7, are tripped by fingers 37, the lead srcew is disengaged, and the cutters are lifted away from the workpiece. The workpiece is then pushed out from the collet by the centre 17.