Improvements in or relating to apparatus for optically gauging profiles

639,131. Optical gauging apparatus. OPTICAL MEASURING TOOLS, Ltd. March 18, 1947, No. 7500. [Class 106 (ii)] An apparatus for gauging by optical means the contour of a profiled work-piece comprises a plurality of contact members mounted in a carriage so as to be presented by the carriage to different faces of the work-piece, means to urge each contact member in turn into engagement with the work-piece, means to cause relative movement between the carriage and the workpiece so that that contact member which is in engagement with a face of the work-piece is caused to traverse the face, a movable index controlled by relative movement between the work-piece and the carriage and an optical system for displaying the movements of the index on a screen bearing a master profile. A turbine blade 12, Fig. 7, is fixed at its root 11 in a plunger 54 urged downwardly inside a holder 47 by a spring 56. The holder 47 is fitted within a sleeve 33 in a bore 32 of a boss 31 of a bracket arm 16 and its flange 48 is connected by a pin 49 to a ring 50 secured to the sleeve 33. A stop 37 on the ring 50 co-operates with two stops 39 on plates 38 secured on a disc 41 secured to the boss 31 to limit the angular movement of the sleeve 33 which may be clamped by a screw 44 threaded into a split portion 45 of the boss 31. The arm 16, Fig. 3, is vertically movable on a pillar 15 between two stops 24, 25 and can be clamped in any desired position. Below the work-holder on a table 14 are two carriages 60, 61, Figs. 3 and 5, the lower one 61 of which is movable towards and away from the pillar 15 by rotation of a knob 63. The upper carriage 60 is transversely movable in ball-bearing guideways on the carriage 61 and has a downwardly extending tubular part 68. Two adjustable ball-tipped stylii 72, 73 project radially inwards over the part 68 and either of them can be brought into contact with the adjacent surface of the depending turbine blade 12 and as the carriage 61 is moved such stylus traverses the contacting surface and the carriage 60 is accordingly moved transversely. A toggle spring unit 81, Fig. 5, under the carriage 61, acts through a bell-crank lever 76 to urge the carriage 60 in such a direction as to keep the stylus against the blade 12. When the contacting stylus reaches the end of the adjacent face of the blade 12 the toggle unit 81 is tripped and the carriage 60 is moved to bring the other stylus against the other side of the blade 12. A roller 132, Fig. 4 (not shown) on an