The invention re ates to improvements in screws such as are employed. in fastening together stove-pipe sections.
It has for its object the provision of a device that can be easily applied and removed and which, when in place, will be secure against accidental displacement.
It consists of a screwof the novel construction hereinafter described, pointed out in the appended claims, and illustrated in the accompanying drawings.
In the accompanying drawings, in which similar reference characters designate corresponding parts, Figure 1 is a side elevation of a screw embodyingthe invention. Fig. 2 shows the screw applled to a -joint. I
The shank a of the screw tapers toward its point 5, and is-provided with a thread 0 square in cross-section. The outer -extremity d of the thread ends a short distance from the point b, and the inner e'xtremity e ends at the shoulder f of the shank a short .distance from the head 9 of the screw. The head 9 is of the usual formation except that it'has 'a beveled inner face h.
Between the heady .and the shoulder f is the neck a of reduced diameter, the latter gemngxlees than the diameter of the threaded In applying the screw the end of one pi e-- section 1s inserted in the end of anot er so thattheir edges overlap, and by means of asultable implement coincident holes are punched through the metal. of the overlapplng edges. The coincidentholes should be of less diameter than thethreaded shank,
but sufiicie'ntly large to admit the point" I). After the holes have beenformed the point 5 is inserted and the shank forced: in until the outer extremity d of the thread engages the-' edges of the metal of the overlapping pipesections. Then by means of ascrew-driver the screw is turned through-the coincident holes until theedges 'of the metal clear the shoulder f and spring around the reduced .neck 5.