Patent GB-330906-A (GB)
IPC: G01B5/20
Abstract: 330,906. Bath, J. March 18, 1929. Linear-dimension gauges; surface and outline gauges. - A machine for measuring threaded members such as screw taps and for indicating variations in size with respect to a standard gauge comprises a yieldable indicating contact member and a positioning device movable to a predetermined position and adapted, through contact with the inserted threaded member, to displace the yielding contact to give an indication. As shown in Figs. 1 and 2, adapted to the measurement of four-fluted taps a table 20 has cross guideways 21, 22, in which are mounted a stand or casing 24, a stand 62, a bracket 81, and a stand 86, carrying respectively contact members 30, 60, 80, and 85. The casing 24 is adjustably secured by means of a clamping screw 25 and carries a bushing 28 in which is slidably mounted a spring controlled plunger 27 to which the contact member 30 is secured. The inner end of the plunger bears on a segment plate 40 forming an angle connection with a spring pressed plunger 42 in a bearing member 43 secured in a split holder 44 by means of a clamping screw 45. The upper end of the plunger 42 engages the piston 49 of an indicating mechanism 50 mounted on a projection 51. A irictionally mounted ring 54 carries the indicating dial so as to effect its angular adjustment. The stand 62 which is adjustable in the guide way 21 has a square section plunger 61 to which the contact 60 is secured, the inward movement of which by the action of a spring 64 is limited by a stop 70 engaging a slot 71 in the plunger. Movement of the plunger 61 to and from the work is effected by a hand lever 75 with a pin 76, Figs. 1, and 3, pivoted in a bearing in the stand 62 and having a member 77 secured thereto, said member being provided with a convex head 78 engaging a slot 79 in the plunger with a limited lost motion. The contact member 80 is fixed to the adjustable bracket 81 but the contact member 85 is yieldingly mounted in the stand 86 and has a projecting end having a pin and slot connection with a bell crank lever 89 connected to a rod 92 slidable in a block 93 pivoted on the under side of the lever 75, the block engaging a collar 95 adjustable on the rod. In operation the handle is first moved in the direction of the arrow a, Fig. 1. to withdraw the contacts 60. 85, and a standard thread gauge is plaoed in position. The bracket 81 is adjusted to bring the axis of the gauge into alignment with the contacts 30, 60 and the stand 62 is adjusted to align the axis with the contacts 80, 85. The casing 24 is then adjusted to compress the spring 34 of the plunger 27 and the frame 43 moved to compress the spring 47 of the plunger 42 whereby the indicating pointer is rotated an angular distance from its normal zero position. The parts are then secured in position and the ring 54 rotated to bring the zero of the scale to this position. The master gauge is then removed and the members to be gauged inserted. As the contact members 30, 60 must engage the taps in different planes, means are provided to vary the amount in accordance with the pitch of the thread comprising shims 26 of different thickness interposed between the under surface of the casing 24 and the guideways 21. In a modified construction for three-fluted taps the plunger 61, Fig. 9, is provided with a swivel member 100 carrying adjustable contact members 101. The member 100 can be turned angularly to correspond to the lead of the thread and clamped in set position by a screw 106. The segment 40 must also be replaced by one which reduces the leverage between the plungers 27 and 42 in the ratio of 3 : 2 in view of the different angular position of the contact members In another construction applied to the measurement of taps with only two sets of teeth the side contact members are replaced by a lever 120, Figs. 12 and 14, pivoted on an adjustable stand 122 and carrying a positioning member 124 with an opening 127 adapted to be axially aligned with the contact members 30 and 60. To permit a tap to be inserted a spring 130 engages an offset arm 131 on the lever 120 to move it to an inoperative position. In setting up the machine the plunger 60 and its stand are adjusted until the tap aligns the graduations 136, 138 on the member 124 and a stand 139 respectively.