GB697061A - Improved screw-cutting attachment for machine tools having reversible working spindles - Google Patents

Abstract

697,061. Screw-cutting attachments. ANGST, F. Sept. 20, 1951 [Sept. 22, 1950], No. 22077/51. Class 83(iii). A screw-cutting attachment for tapping or screwing rotating work has a pair of dogclutch members 28, 32 journalled on a stud 16 screwed into a tool-holder 7 and having a spring 34 tending to press them apart, a set of balls 29 fitted in conical recesses 27 in the toolholder 7 and in the clutch member 28, and spring-loaded balls 37 fitted in the clutch member 32 and engaging a conical part 35 of the stud 16. A pair of rollers 43 are also fitted on the clutch member 32 and slide in a wide recess 44 in the body 1, their forward movement, and therefore the length of thread cut, being limited by an adjustable screwed collar 45. When the tool contacts the rotating work, it is held against rotation by the clutch and by the rollers 43 bearing against one side of the recess 44 in the stationary body but feeds forward according to the pitch of the screw being cut. The tool-holder is initially supported at points 5, 11 but is tapered between these points so that, as it feeds forward, it is only supported at point 11 and by the work, and can oscillate with work which is not running true. During forward feed, the wedging action of the balls 29 in the conical recesses forces the tool-holder and clutch member 28 apart by a clearance a but, when the rollers 43 meet the collar 45, the clutch member 32 is held back while the other member 28 moves forward until it disengages. The tool-holder and member 28 are now freely rotatable and the spring 34 takes up the clearance a so that the two clutch members are definitely separated and cannot engage because of vibration. Since the stud 16 has moved forward with the clutch member 28 relative to the clutch member 32, the balls 37 now ride over grooves 36 in the portion 35, but when the work-spindle is reversed, they rotate the member 32 until the rollers meet the other side of the recess 44, where they move forward into a small cut-out 46 and allow the clutch members to re-engage and again prevent the tool rotating. The screw 41 in the end of the stud 16 holds the member 32 against rearward movement which would render the balls 37 ineffective. By moving the collar 45 so that the cut-out 46 adjoins one or other side of the recess 44, right- or left-hand threads can be cut.