257,670. White, A. E., (Heald Machine Co.). June 4, 1925. Round holes, enlarging and trueing; gauges; trueing rotating tools. - A machine for internally grinding cylindrical surfaces comprises gauging- means whereby, upon the work approaching the finished size, the grinding-wheel is trued, to take the finishing cut, and upon the work reaching finished size the wheel is moved tc. an inoperative position to allow of removal of the work and insertion of a new piece. The grinding-wheel is reciprocated by fluid pressure means controlled by electrical circuits operated by the gauging means. The machine, Fig. 1, consists of a reciprocatory carriage 1 carrying, grinding-wheel head 2, the work being rotatably mounted in a stationary head 3. The table is reciprocated by a piston 8 in a cylinder 7, pressure fluid being supplied from a pump through piping 11, a throttle valve 19 adjustable by a handle 20, and a reversing valve 12, the fluid being drawn from, and exhausted to, a tank 17. The valve 12 is moved by adjustable dogs 30, 31 on the table engaging a lever 28 which moves a hand lever 25 on a shaft carrying the valve. The grinding-wheel is fed automatically at each reciprocation of the table by a stop 34 operating ratchet gear on a cross shaft 32. The gauging-mechanism comprises a lever 37, Fig. 4, carrying a point 38 which engages with the work, the lever being mounted to oscillate on two crossing springs 39, 40 carried by a box 44, the arm 37a of the lever having an adjustable screw 50 which engages an indicator lever 46 pivoted at 47 in the box and giving magnified readings on a scale 48; adjustment of the screw 50 brings the lever 46 to any required reading on the scale. The lever carries two electrical contacts, one 55 being directly on the lever and the other 54 on a spring 58 carried by the lever, the contacts contacting with stationary terminals 57, 56 on the box 44 when the lever is at zero reading. The box 44 is adjustable longitudinally on a bracket by means of a screw 60, and is held in position by bolts. The bracket is carried by a spindle 64 having a coned part bearing in a corresponding recess in a sleeve carried by a bracket 71 adjustably mounted on the machine frame. This arrangement enables the box 44 to be swung to an inoperative position, after completion of grinding, by means of an arm 80 clamped by a bolt 79 to the spindle 64, the arm being engaged by a cam bar attached to the carriage. When the slide 1 makes an extended movement after the finishing cut has been taken from the work, a spring returns the gauging-mechanism to the operative position as determined by a lug which contacts with a fixed stop on the bracket 71. The mechanism also may be moved to inoperative position by loosening the bolt 79, a surface on the bracket engaging a lug 87 when the mechanism is back in position. In order to prevent forcible engagement between the point 38 and the work, the lever arm 37<a> is held by a bolt 90 and a projection on the shaft of a handle 88, until when the mechanism is swung into operative position. When the work is ground down sufficiently for the points 54, 56 to make contact, the slide 1 makes an amplified stroke to the right and trueing- mechanism is brought into position to true the grinding-wheel. This action is brought about by the energization of an electromagnet 121, Fig. 8, which attracts an armature on a lever, one arm 126 of which lifts a latch 107, pivoted to a block 104 on the slide from engagement with a block 102 on which the dog 30 is mounted, and allows this to move relatively to the slide 1 until stopped by the block 104, when the dog 30 moves the lever 28 and reverses the motion of the slide. The circuit of the electromagnet 121 is through a two-way switch 117. To restore the dog 30 to its latched position, a spring-pressed lever 127 is provided having faces 129, 130 which engage the block 102 and hold it stationary during the return or left-hand travel of the slide, thus allowing the latch to resume its engagement with the block 102. Simultaneously with the commencement of the single amplified reciprocation of the table 1, an adjustable diamond dressing point 145 is moved into the path of the wheel; this movement is effected by an arm 133 of the lever 126, the arm moving a valve 135 in a cylinder 138 to admit fluid from a pipe 141, Fig. 10, to a cylinder 144 in which is a piston 143. The piston moves a bell-crank lever 146 carried by a shaft 147, the lever being connected by a rod 151 to a rotatable member 154 carrying the diamond point; a handle 158 serves to swing the point manually away from the wheel when desired. Alter the wheel has passed forward and back across the diamond, this is raised automatically and is maintained out of the dressing position, the movement being caused by an adjustable cam bar 166 on the table 1, which bar engages a roller 167 on the belt-crank lever 146, and positively moves this to lift the dressing-device to the inoperative position. In order to cause the table to travel at reduced speed during dressing of the wheel and in the finishing cut on the work, a valve 174 is provided in series with the throttle valve 19, the valve 174 comprising a rotatable plug with a transverse orifice which may be brought by rotation of a shaft 181 carrying the valve into or out of register with ports 178, 179 the piping 11, to impose more or less resistance to the flow of fluid. The valve shaft 181 carries a lever having arms 183, 184, the arm 183 being connected by a link 185 to a lever 186 mounted on the shaft 147 carrying the bell-crank lever 146. The link 185 is moved by lugs 187, 188 thereon, and, by adjusting these, the speed of the table remains at the reduced speed during the finishing cut as well as during dressing. During the amplified dressing stroke of the table 1, a projection 189 moves over the switch 117 and opens the circuit of the magnet 121, so that the final and finishing strokes are of normal length. When the work is to size, the points 55, 57 contact and the circuit of a magnet 193, Fig. 8, is closed, and the magnet attracts an armature 195 on a lever pivoted at 196. An arm 197 of this lever then strikes the dog 30, which is pivoted at 198 on the block 102 and lifts it so that it does not strike the lever 28; the table thus continues to move to the right to carry the wheel completely out of the work and past the dressing device, the table being finally stopped by movement of a lever 202, Fig. 2, which operates a valve 203 to' relieve the piston 8 of the fluid; the movement of the table is increased by a cam bar 204 secured to the block 102, which strikes a lever 205. This lever operates a valve 207, Fig. 2, which connects the cylinder 7 directly to the piping 11 through a pipe 209. The valve 174 is returned, during the final stroke, to its normal position by a part 210 of the cam bar 166, which lifts a member 212 connected by a link 215 to the lever arm 184; the movement of the table also rocks the gauging. mechanism to the inoperative position.