Patent GB-742962-A (GB)
Title: An internal diameter gage
IPC: G01B5/08
Filed: 1953-09-07
Abstract: 742,962. Gauging departure from standard form. SUNNEN, J. Sept. 7, 1953 [June 23, 1953], No. 24658/53. Class 106 (2). A gauge for determining the amount by which the diameter of a circular bore departs from a stated nominal diameter, comprises three horizontal contact holding fingers, one, the sensitive gauging finger, being resiliently mounted on two horizontal spring strips extending normally to the axis of the fingers, the finger being linked to a dial indicator gauge, a second, the adjustable gauging finger, being movable horizontally and transversely to the axis of the fingers, and a third, the centrallizing finger, being movable vertically and transversely to the axis of the fingers, the centrallizing finger being linked to the adjustable finger so that the distance it moves vertically is half the distance the adjustable finger moves horizontally, and means are provided for locking the position of the second two fingers relative to the case. In Figs. 5, 6 and 9 a plate 42 rests on a projection 30 of the casing 10 and has two raised bearing surfaces 44 (Figs. 24, 25, 26) on which slide a plate 46 (Figs. 21, 22, 23) guided by vertical pillars 56, 58 attached to the fixed plate 42, and controlled by the nut 74, rotatably fixed in the side of the casing, which engages the thread 72. Pillar 58 also provides an abutment for a spring 90 which, in conjunction with a nut 100 and a handle 108, locks, by vertical pressure, the sliding plate 46 to the fixed plate 42. Fixed to the sliding plate 46 by two screws 120 is the adjustable finger which has a rear portion 122 (Fig. 8) and a front semi-circular cylindrical portion 124 (Fig. 12). The sensitive gauging finger has rear and front portions 136, 138, respectively and is fixed by screws 152 to the ends of two spring strips 140 (Figs. 17, 18) which are fixed at their other ends to the fixed plate 42 by screws 148. The spring strips are steadied from below by pieces 146 (Figs. 19, 20), and allow the sensitive gauging finger, which is biased from a horizontal position by a spring 179, to pivot about a horizontal axis parallel to the axis of the fingers, to control a plunger-type dial gauge 172 which thus normally indicates a non-zero reading, indicating zero only when the sensitive gauging finger is horizontal. The centrallizing gauging finger 188 is fixed by a screw 194 to a second sliding plate 192, which is so supported by strips 200 and a spring, that it slides in a vertical plane always in contact with the front cover 10, with the surfaces 214 on two projections 216 on the cover 10, and with the plane surface 128 of the adjustable finger. As the nut 74 is turned plate 46 slides on plate 42 and carries the adjustable finger with it, which bears against the plate 192 and causes it and the centralizing finger 188 to move diagonally upwards through a vertical distance equal to half the horizontal distance moved by the adjustable finger and thus the centralizing finger always remains vertically above a point midway between the sensitive and adjustable fingers and in such a position that it lies on the circle having the sensitive and adjustable fingers as diametrically opposite points. The fingers are tapped to receive two sets of contact points, a smaller set 234, 236, and a larger set 254, 256 (Figs. 11, 12), and the top edges of the sensitive and adjustable fingers are ground horizontal. Initial setting of points.-A device, shown in use in Figs. 31 and 32 is used to adjust the contact points in the fingers so that they lie on a circle and consists of a thick plate 306, having accurately positioned contacts 332, 334, and a central magnetic contact 326. For setting the small set of contact points (Fig. 31) the adjustable finger is moved out sufficiently far for the surfaces 320 of the plate to rest on the horizontal surfaces of the sensitive and adjustable fingers and is then moved out still further until, with the plate still resting on the fingers, the contact points 234 touch the contacts 334 of the plate. The centrallizing contact point is then adjusted, with the aid of the magnet, so that it touches the magnet. The points are then lying on a circle. A similar process is used for setting the larger contact points, except that the plate rests on the stems 261 of the contact points in the sensitive and adjustable fingers (Fig. 32) and that the side 308 of the plate which was the front side when setting the small points is now the back side and is in contact with the front cover-plate 34. Operation.-For gauging a bore the contact points are set to the minimum diameter of the bore, which, if the bore is to receive a pin will be the diameter of the pin, and this is most easily done by using the device shown in use in Figs. 27, 29 which consists of a back plate 278, with an opening 282 for the contact points, a block 284 attached to the back plate by screws 286 and to a second block 298 by a screw 290 which passes through an untapped hole 288 in the block 284, both blocks having longitudinal holes 304 to reduce weight. Two pins of the appropriate size are clamped between the blocks and the device is placed over the contact points, the whole of its weight being taken by the centrallizing finger. The adjustable finger is then moved out as far as possible until a zero reading is indicated on the gauge and is then locked in position by the handle 108. The dial of the gauge can be advantageously rotated so that the indicated reading on the gauge (previously zero) is the actual clearance required between the pin and the bore so that the dial gauge will indicate zero when a bore having this correct clearance is gauged.