Patent GB-574400-A (GB)
Title: Improvements in or relating to methods of and devices or machines for drilling
IPC: B23B47/34
Filed: 1943-08-18
Abstract: 574,400. Drilling. BASTIAN-BLESSING CO. Aug. 18, 1943, Nos. 13451 and 13452. Convention dates, Aug. 20, 1942 and April 26, 1943. [Classes 83 (ii) and 83 (iii)] In drilling metals, alloys, elastomers and plastics a relative reciprocation, of small amplitude, between drill and work is superimposed upon the continuous feed to cause the cuttings produced to be severed into small sections. The reciprocation preferably takes place once during each revolution of the drill and is less than 0.04" in magnitude. Each hump 8, Fig. 5, left by one edge of a twist drill is removed at the next drilling stage by the other edge. If it be desired to vary the angular displacement between tool and work between two successive separations the work is preferably rotated as well as the drill, in the same direction if smaller, and in the opposite if larger chips are desired. The separation of drill and work enables the lubricant to get complete access to the working face and to cool the extreme cutting edges of the drill whilst the breaking up of the chips facilitates their discharge along the flutes of the drill without scoring or bell-mouthing the hole, and jig bushes may be used in close contact with the work. Long holes may be drilled in one stage without requiring complete withdrawal for discharge of cuttings and one or more turret stations occupied by drills, when drilling holes in stages, may be set free. The reciprocation may be effected by attachments to existing machines. In one form a taper shank 38 for engagement in a drilling-machine spindle has a tongue-and-slot engagement at 43 with a spindle 41 carrying the drill chuck or socket. The spindles each carry the inner race of a ball bearing, the outer races 33 being mounted in a two-part casing 22 having an arm engaging the frame of the drilling- machine to prevent rotation. The spindle 41 has a collar 45 carrying a headed pin 53 that engages a cam 47 secured in the casing by setscrews 48. A spring 46 confined between the lower ball race 40 and the flange 45 keeps the pin in engagement with the cam which supplies the reciprocation, the continuous feed being imparted to the spindle 38 by the ordinary feed motion of the machine. The pin may be replaced by a roller and the lower spindle 41 may have a central axial extension extending into a bore in the upper spindle and shank 38 to maintain good axial alignment between the two parts. In a modification, the lower spindle part 97, hollowed at 100 for lightness, telescopes in the upper 94, and carries a transverse pin 101 that passes through slots 104 in the part 94 serving both to transmit drive and adjustably limit the reciprocation. The casing 77 has screwed connection with upper and lower caps 88, 115. The spindle 94 carries the inner races of two ball bearings, the outer races being separated by a distance sleeve 91 and mounted in the cap 88 and casing 77. A spring 106 is confined between washers supported by the inner race of the lower bearing and by the pin 101. The casing 77 is hollowed out to receive two follower rollers 52a mounted on eccentric sleeves 120 on pins 84 rotatable by a half hoop 123 having an adjusting screw connection 127, Fig. 22 (not shown) with an abutment carried by the cap 115, which contains the cam 47a connected by pins 110 with a flange 108 on the spindle 97. The cam has two tracks each engaged by one of the rollers 52a. In a modification, the spindle 97 is relieved to engage the spindle 94 at its lower end only, additional engagement at the upper end being secured by an interposed ground sleeve. The cam is mounted on the pin 101 and the lower ball race is mounted in the cap 115 increasing the axial distance between the surfaces that maintain alignment. The spindle 97 is screwed to receive a nut carrying an index mark registering with graduations on the lower end of the spindle 94 to provide adjustment for the extent of the axial reciprocation. A lock nut is provided to secure the adjustment. When the device is incorporated as a permanent part of a drilling- machine this adjustment is preferably sufficient in range to prevent reciprocation entirely, to permit drilling by the usual method when required. A further modification in which the bearings and cam have the same relative position as Fig. 21, has the parts designed for production in automatic screw machines. The outer part of the casing is formed from tubing and is fitted with a nipple for grease lubrication, passages being provided below the lower ball race to permit access of grease to the cam rollers. Mounting chucks and sockets.-Alignment of the drill socket 112, Fig. 21, with the spindle is secured by cylindrical surfaces 133 above and below the threaded portion 113. A drill chuck 17, Fig. 23, not having a taper shank, is mounted by a screwed dowel 135 hexed at 136 in a socket 112a itself mounted on the surfaces 133, 113. Metal shavings.-The cuttings take and retain the form shown in Fig. 19, facilitating expulsion by the lubricant delivered to the point of the drill, for subsequent disposal and reclamation.