764,671. Drilling-and-tapping machines. HOWE & FANT, Inc. Feb. 21, 1955 [March 18, 1954], No. 5108/55. Class 83 (3). [Also in Groups XXIV and XXXVII] A machine tool, particularly a drilling machine, comprises a spindle 26 rotatable in a quill 23, a turret 58 carrying tool-spindles 69, means 33-36, for driving the spindle 26 at different speeds, stops 96 for limiting the feed of spindle 26, and means, operated by indexing the turret, to make effective the stop 96 for the appropriate tool-spindle and to adjust the driving means to a pre-selected speed for the latter tool-spindle. The spindle 26 is rotated by a variable-speed belt gearing 33, 34, 36 driven by a three-phase, reversable electric motor 35 having low- and high-speed windings energized selectively by the setting of a dog 52, Fig. 4, for each tool spindle. The dogs are carried by a gear 49 and trip a lever 56 (Fig. 3, not shown) when the high-speed winding of the motor is used. The ratio of the belt-gearing is varied by changing the distance between the driving-discs 34 on the motor shaft by stop screws 47 carried by a disc 46 on the piston-rod of a pneumatic-jack 40 which supports the lower disc 34 in a bearing housing 37 carried by a yoke 38. The stop-screw 47 for the tool spindle in operative position abuts a plug 50 in the gear 49 to set the spacing of the discs 34, the other stop-screws entering passages in the gear which may be rotated to align the plug 50 with another of the stop-screws following withdrawal of the screws by jack 40. A valve 43 supplying the jack 40 is operated to withdraw the stop screws through contact between its plunger 43a and the turret as the latter is raised for indexing and bears against the spindle-head 22a. In this position, a tang 81, Fig. 11, on a shaft 79 carrying a gear 80 meshing with a ring-gear attached to the indexable part 68 of the turret, engages a socket 82 in a shaft 83, Fig. 2, carrying a gear 85 meshing with a gear 86 rotatable on the sleeve 23 and forming the lower member of a cage, the bars of which are threaded for the feed stops 96 and the top 98 supports switch-operating dogs 99. Rotation of the part 68 during indexing of the turret rotates the cage 86, 95, 98 and the gear 49, through an intermediate gear 105, to adjust the drive speed and position the stop for the operative tool-spindle, a spring-pressed ball 93 entering a slot 86d and a pin 92 on the sleeve 23 entering one of the passages in the bore of the gear 86 when the turret is correctly indexed. The tool-spindles 69 are mounted for self-alignment in the turret on spherical seatings 74, and the turret, which is supported on a spring 60 resting on a collar 59 fixed to the bottom of the sleeve 23, is raised by a rack-andpinion 24 assisted by a balance-weight on a cable 118. The feed-stops 96 co-operate with a projection 29a, Fig. 1, carried by the sleeve 23, and rotation of the turret is prevented by a bar 84 in the spindle head 22a. A motorswitch 111 is housed within the hub of the feedlever 110, Figs. 2 and 9, and is operated by a key 116 on the feed-shaft upon slight relative movement between the hub and the shaft, and a further switch is operated by a lever 104 disposed beneath the dog 99 in operative position and acts to reverse the motor for high-speed running. The switch operated by the lever 104, switch 111, and the contacts of a relay are connected in parallel to the coil of a further relay for reversing the motor, the control-circuit, Fig. 13 (not shown), also including the switch operated by the dogs 99 through a plunger 101, a start-and-stop switch, a switch for changing the speed of rotation of the motor and two further relays controlling high and low speed running of the motor. The motor can be reversed by turning the feed-lever to close the switch 111 and raise the machine spindle. Tapping. During tapping, the motor can continue to run after the projection 29a on the sleeve has engaged a feed-stop 96, and causes the cage 86, 95, 98 to be displaced against the influence of springs 89, Fig. 7, until a stop 91 is reached and the dog 99 in operative position actuates the switch-lever 104 and the reversing- relay to reverse the motor automatically. Energization of the reversing-relay and reversal of the motor produce a surge of current which momentarily closes the contacts of the relay in parallel with the switch operated by the lever 104 and that in the hub of the feed-lever, so that although the switch operated by lever 104 is opened as the springs 89 return the cage, the machine is protected for this short period against the motor again being reversed by de-energizing the reversing relay through opening switch 111 by turning the feed-lever in the feed direction, switch 111 having closed upon relative movement between the feed-lever and its shaft 25 caused by reversing the motor. Sockets. A socket 63, Fig. 12, for driving the tool-spindles 69 is fixed to the machine-spindle 26 by a collar 62 and a pin 64 and has a tapered bore 65 to engage the spindles 69 and spring- pressed plungers 66 which effect a positive drive in recesses 77a in the tool spindles if the drive tends to slip. Alternatively, the tool spindles may be formed with socket ends for engaging a spigot-driver on the machine-spindle.