480,410. Boring-bar machines. KRAUSE & CO. AKT.- OES., E. April 19, 1937, No. 11055. Convention date, April 23, 1936. [Class 83 (iii)] A boring-machine having one or more spindles, particularly for operating on the bearings of engine crank-cases, gear-boxes, &c., has the spindles supported vertically at both ends, driven from below, and so coupled with the driving shafts that they may be withdrawn upwardly through the work. The machine comprises a base 1 containing the driving mechanism for two vertical shafts 4, Fig. 1, and carrying a work support 33. A pillar 2 carries a vertically adjustable head 21 for the upper bearings of two boring bars 7 which are releasably attached at 4<1> to the driving shafts 4. The upper bearings 8, Fig. 2, of the boring bars 7 are splined thereto so as to rotate therewith, but are axially fixed in the head and have axial slots 9<1> therein through which the cutters 71 of the bars may pass. The shafts 4 and bearings 8 are laterally adjustable to enable the spacing of the boring bars to be varied. A transverse shaft 13 provided with a handle 12 carries a bevel gear 15, Fig. 2, connected by a bevel gear 16 to a spur gear 17 engaging two spur gears 10, Fig. 1, freely rotatable about the boring bars 7 and rotatably and slidably mounted in bearings 11 in the head 2<1>. Springs 18, Fig. 3, tend to press the gears 10 downwards but are prevented from acting by levers 19 and pins 20 engaging cams 14 on the shaft 13. Rotation of the handle 12 to a definite angular position rotates the cams 14 to allow the gears 10 to descend and engage keys on the boring bars whereby the bars are rotated to bring the cutters 7<1> in line with the slots 9<1> of the bearings 8 so that the bars may be withdrawn axially from the work 35. This axial motion is effected by means of yokes 25 yieldingly mounted on a slide 27 carrying a rack engaging a pinion 23 connected by a shaft 22 and gear 21 to the gear 17. Actuation of the handle 12 thus moves the yokes yieldingly into contact with grooves 26 on the boring bars and the latter are then raised clear of the work to allow changing thereof by means of an electric motor 28, controlled by push-buttons 41, 42 and connected by worm gearing 29 and pinion 30 to a rack 31 attached to the carrier 271 of the slide 27. The motor is switched off automatically at the end of the traverse. The work 35 is held by a spring clamp 40, Fig. 3, and the cams 14 on a table 3 pivoted to the support 33 at 34 and located in the operative position by means of a stop 37 thereon engaging the pillar 2. In one direction of rotation of the shaft 13, a lever 39, Fig. 1, thereon engages a bevelled surface on the stop to press it against the pillar and in the other direction a lever 38 engages a bevelled surface on the opposite side of the stop to rotate the table 3 slightly about the pivot 34, simultaneously with release of the clamp 40, in order to allow the cutters 71, which have then been placed below the grooves 9<1> in the bearings 8, to clear the bores formed in the work when they are withdrawn axially. The table 3 may also be rotated through 180‹ on the support 33 to allow the bores formed therein to be measured, and the boring bars may then be lowered to enable the cutters to be adjusted, after which the bars are raised again and the table 3 returned to operative position. The rotation and axial feed of the shafts 4 are controlled by a hand lever 5, the change from quick approach to cutting feed and reversal of feed &c. being actuated automatically by dogs on a cam plate in a casing 6. The work is secured to the table 3 by hand-operated clamps and levelling bolts, centring bores, &c. Balancing parts.-The head 2<1> carrying the upper bearings for the boring bars 4 is balanced by means of a chain 32<1> and a weight sliding in the pillar 2.