GB602652A - Improvements in or relating to riveting - Google Patents

Abstract

602,652. Blind riveting. BRITISH UNITED SHOE MACHINERY CO., Ltd., and COOPER, B. P. Dec. 19, 1945, No. 34372. [Class 43] A mandrel for blind riveting has a head, a tapering part (increasing in cross-section towards the head) of length not less than half the thickness of the workpiece, most of this part being received in that part of the set rivet which lies between the faces of the work, a protruberance on this part being arranged to interlock within the work with the metal of the rivet during setting. The mandrel M has a head 1 with a conical top 5 and a shoulder 3 where it joins the rest of the mandrel, as in Fig. 7 of Specification 558,156. It has a cylindrical main stem 7 (to be gripped by a rivet-setting tool as described in Specification 348,818) which extends up to a location X; from here to the shoulder 3 is a portion 9 which would be frusto-conical, co-axial with the stem 7 and increasing in cross-section towards the head 1, except for a protuberance P on a part thereof; the length of this tapering part 9 is greater than the diameter of the stem 7, being at least 1¢ times that diameter, and is not less than about half the thickness of the workpiece. At the upper end of the protuberance is a narrow annular shoulder 11, between which and a location Y there is a cylindrical part 13, the radius of which is about equal to the radius of the part 9 where it joins the head 1; diametrically opposite one another and extending downwards from the part 13 are two projections 15 of decreasing width and thickness which finally blend into the part 7 at the location X. The mandrel is made as described in Specifications 501,415 and 558,156. The hollow metal rivet R, made by pressing from sheet metal stock, has a frusto-conical head 19 for reception in a countersunk hole in a workpiece, and a tubular barrel with a cylindrical outer surface and an internal bore whose diameter increases slightly from the head 19 towards the tail while the thickness of the metal decreases; it thus corresponds to the tapered part 9 of the mandrel. When the tail end of the rivet is pierced to open it a slight step is left inside the tail end of the bore; the internal diameter of the rivet at its head end and at this step is the same as the diameter of the stem 7 of the mandrel, and the distance between the shoulders 11 and 3 is greater than the greatest diameter of the internal bore of the rivet. During assembly the mandrel passes into the rivet until the location X is reached when slight axial pressure causes the parts to be held frictionally together; the parts are now threaded into aligned holes in the layers 23, 25 of a workpiece, the total thickness of which is about the same as the distance between the location X and shoulder 3; the head 19 of the rivet is held up to the layer 25 and a rivet-setting pull is applied to the mandrel stem 7 so that the head 1 expands the tail end of the rivet. During this operation the protuberance P is first drawn through the tail end of the rivet, then, in view of the tapered bore of the rivet, presses with gradually increasing force against the metal thereof, the inclined shape of the projections 15 facilitating entry and also aiding the gradual build-up of pressure. Continued movement of the protuberance causes the metal of the rivet to flow back over the shoulder 11, so that it is firmly locked therein at a locality within the work much closer to the head end of the rivet than to the tail when the setting is completed. The projecting part of the stem 7 of the mandrel is now cut off flush with the head 19 of the rivet; this may be a separate operation, or a rivetsetting tool as described in Specification 564,383 may be used. The shape of the head 1 causes the rivet to lap over it slightly, thus reinforcing the action of the shoulder 11 in retaining a portion of the mandrel within the rivet. The mandrel may have a constriction 29 in its stem at which it is intended to break when the rivet is set. Specifications 286,471, [Class 43], and 424,241 also are referred to.