GB567429A - An improved machine for screw threading nuts or tubes by tapping - Google Patents

Abstract

567,429. Tapping nuts. ROBERTS E. H. May 10, 1943, No. 7371. [Class 83 (iii)] A machine for tapping nuts &c. has a screwthreaded spindle carrying the tap and provided at its upper end with a perforated plate 8 driven by pins 7 on a corresponding plate on the spindle of the electric motor 2. Gearing 13 drives a gear 9 at a reduced speed, the boss of the wheel 9 having a squared thread screw engaging the threads on the spindle. A plate mounted in the spindle between ball thrust bearings carries two rods projecting vertically upwards, one of which passes through a fixed guide, to prevent the plate from rotating, and carries an adjustable stop screw 28 that engages the arm 29 of a mercury switch when the required depth has been tapped; the tap is then unscrewed and when sufficiently clear of the work the other rod 26 engages a stop switch 31, in the circuit of reverse drive leads only, thus bringing the spindle to rest. After the work in the holder 3 has been changed, the machine is restarted by raising the switch arm 29, the switch 31 being reset by a spring. A boss is secured to the shank of the tap and this carries two plates apertured to engage two pins projecting from a corresponding member secured to the spindle, the parts being secured by nuts on the ends of the pins. The parts are supported by a column 19 and a number of these columns are mounted in circular formation in discs 51, 52 carried by a central hollow column 36 rotating on a roller thrust bearing 49 and in a journal bearing 50. The drive is preferably by electric motor (not shown) and is at such a speed that an operator stationed at one spot is able to change the work and restart the spindle during the interval required by the spindle to pass his station. A hopper 46 secured to the upper part of the column surrounds its funnel end to which cutting lubricant is delivered by a pipe 37 leading from a pump (not shown) supplied from a sump 42 by a pipe 43. A fixed valve 41 in the column supplies a series of ports connected by pipes 39 passing in part down the column and leading to delivery nozzles 40, the valve being so set that only the spindles that are tapping receive lubricant. Any overflow from the funnel enters the column by holes 47 and escapes at 48 to the sump together with any leakage past the valve 41. Current to the motors is supplied through slip rings 55. Lubricant draining from the work is collected at 46 and passed to the sump at 45.