GB764879A - Method and apparatus for machining and relieving stresses in a workpiece - Google Patents

Abstract

764,879. Copy-turning; milling; chucks. CREEK, J. O. Jan. 10, 1955, No. 697/55. Class 83 (3). [Also in Group XXIII] A method of relieving stresses in a long slender workpiece, such as a gas-turbine blade, during machining (e.g. milling or grinding) comprises rigidly clamping the work at opposite ends, rotatably driving the work at both ends, freeing one end to permit that end to be displaced as a result of stresses set up during machining, and then reclamping in its displaced position for further machining without stopping the rotation of the work. The lower end of the work 13, Fig. 1, is gripped by a chuck 12, the jaws of which are operated by a rod 14 mounted within the lower spindle 5. The chuck is secured by a threaded ring 11 and the spindle rotated by a gear 9 from a driving shaft 10. The same shaft drives the upper spindle 1 through a gear 8. The upper spindle is mounted in antifriction bearings 2, 3 and has its hollow interior opened out at one end to form a cylinder 15 for a piston 19 which may be adjusted by air pressure through an annular gland 24 to suit blanks of different lengths. A further piston 27 within the piston 19 is supplied with air through an annular gland 32 to actuate a spring-returned push-rod 33 with an enlarged head 30. A chuck 20, Fig. 2, for the upper end of the work, comprises a fixed jaw 40 and a pivoted jaw 45 moved by a cam surface 46 formed in the slotted end of a draw-rod 25. The latter is forced upwardly to close the jaw by a compression spring 35 which bears at its upper end on a thrust washer 37 and adjusting sleeve 38. The chuck jaws are held in position by a split retainer-ring 41 and a ring- nut 43, and the engaging surfaces of a shoulder 40b and end face of the chuck body form friction surfaces of a clutch which slips when pressure is applied to the upper end of the draw-rod 25. The chuck 20 fits into a tapered recess 18a in the upper spindle and is retained by a nut 21. The head 30, Fig. 1, of the push-rod 33 has a ball thrust bearing and is adapted to be brought down into engagement with the end of the chuck draw-rod 25. The chuck and the drive clutch may thus be released while the work is rotating to allow the work to rotate relative to the upper spindle to relieve stresses set up during machining. A modified chuck arrangement allows lateral as well as rotative movement of the work to relieve stresses. The upper end of the workspindle 1 is adapted to have interchangeably-mounted thereon a pattern 16 and a cam 17 for control of the position of the rotary cutter (not shown) during the machining operation.