Patent GB-762244-A (GB)
Title: Improvements in or relating to gauge for threads
Filed: 1954-07-26
Abstract: 762,244. Gauging screwed threads. SHEFFIELD CORPORATION. July 26, 1954 [July 30,1953], No. 21729/54. Class 106 (2). Gauges for tapered male or female threads give direct indication of the correctness of the particular feature being gauged from the depth of interengagement of the gauge and the thread. A gauge for testing the taper and pitch circle diameter and axial length of a female thread (Fig. 5) comprises a screwed plug 81 carried on a shaft 82 to which are secured a finger piece 83 and scale element 85. The shaft 82 is rotatable and slidable within a shaft 88 carrying a screwed plug 87 and to which are secured a finger piece 89 and scale element 92. A sleeve 95 is slidable on the shaft 88 and is biased away from the plug 87 by a spring 98. The threads on the plugs 81, 87 are relieved at the root and crest. In gauging, the plugs 81, 87 are screwed hand tight into the thread of the workpiece. The taper of the latter determines the distance between the plugs and its correctness is indicated by the position of the end face 91 of the finger piece 89 relative to a band 86 on the element 85. The width of the band 86 is proportional to the allowable tolerance. The sleeve 95 is now slid forwards to engage the end of the workpiece and the position where its end face 99 intersects a helical scale line 93 gives an indication in fractions of a turn, of the pitch diameter accuracy. In a gauge for testing the crests of a female thread (Fig. 6) the screwed plugs are replaced by a plug 106. The plug is entered first loosely into the thread when it gives an indication of any ovality by wobbling, and then tightly. The sleeve 101 is pressed against the end of the workpiece and the position of its edge 111 relative to a helical band 109 noted. The band 109 is of a thickness corresponding to the allowable tolerance, and the edge 111 should intersect the axial marking ccrresponding to that obtained on the first described gauge in respect of pitch circle diameter, within the tolerance band. Similar gauges are described for testing the thread root and the bore at the inner end of the thread, the plug 106 being replaced by a threaded plug, and a cylindrical plug having a tapered end rim respectively (Figs. 7, 8, not shown). The gauge for testing male threads for taper and pitch circle diameter (Fig. 1) comprises relatively moveable internally threaded rings 42, 43 which are engaged with the thread, hand tight. The correctness of the taper is given by markings at 42a, 43a indicating the relative positions of the rings, and a plunger 52 is advanced to engage the workpiece, the pitch circle diameter reading being given by the intersection of an edge 58 with a helical scale 56. Crest and root truncation gauges for male threads are also described (Figs. 2, 3, not shown), differing from the taper and pitch circle diameter gauge in that the rings 42, 43 are replaced by conically bored or internally screwed elements respectively, secured to the sleeve, such as 45, in which the plunger slides. In a further embodiment (Fig. 9) rollers 155 which may carry screw threads, as shown, or smooth conical surfaces, are rotatably mounted on a sleeve 141 for engagement by a male thread, a plunger 142 measuring the depth of engagement as before.