FLOWDRILL, PARTICULARLY ADAPTED TO BE USED IN A HAND DRILLING MACHINE

Abstract: This flowdrill (1), which provides holes in sheet material through the heat developed by friction between the sheet and the tapering drill shaft (2, 3, 4), is adapted to be used in a hand manipulated drilling machine. Thereto the drill is provided with cutting edges (7) along part of the surface extending from close to the drill tip.

Description: Title: Flowdrill, particularly adapted for use in a hand drilling machine. The invention relates to a flowdrill, having a shaft with a substantially smooth, tapering effective end. Such flowdrills are known, e.g. from the French patent 1.189.384, the Dutch patent 160.499 and the European patent 57039. They operate satisfactoraly in larger stationary drilling machines, in which they may be brought into engagement with a workpiece by a sufficient axial force, so that so much heat is generated due to the friction with the usually sheetlike workpiece, that a beginning of the hole to be drilled is formed. The use of a flowdrill in a hand held drilling machine is practically impossible since then the user would have to produce himself the axial feed force. It has now appeared through experiments that this disadvantage may be overcome if for this purpose a special flowdrill is used, namely a flowdrill in which one or more cutting edges have been provided on the effective shaft surface, adjacent to the tip of the tapered portion. Thereby a beginning of the hole is generated by the cutting edges and this quickly and without a strong axial feed force, Thereafter the drill moves downwardly into the hole to such a distance that the cutting edges have passed the hole so that the drill furthermore operates like a conventional flowdrill. The drill according to the invention likewise may be used with advantage in a stationary drilling machine, in which the obtainable feed force is not sufficient to quickly produce a hole by means of a conventional flowdrill. Preferably the cutting edges are formed in the shaft tip by means of recesses having sharp edges, which are provided in the tip surface. In most cases with the drill according to the invention the axial length of the shaft portion having the cutting edges will have a length equal to about 1/3 of the hole diameter to be provided. For it is, if this length is too small, there is no sufficient space for leading away the chip which is formed during cutting, whereas if the length of the cutting edge or edges is too large, too much material is cut away, so that the sleeve, which is formed, as will be further described below, becomes too thin. The invention will be further explained below with reference to the drawing, showing as an example an embodiment of the flowdrill according to the invention. Figure 1 shows a side view of the flowdrill. Figure 2 is a view from below of said drill. Figure 3 shows a cross-section of a hole, made by the flowdrill according to figures 1 and 2 , namely the left part of the figure after the passage of the drilltip and the right part of the figure after the passage of the complete drill. The flowdrill 1 as shown in figure 1 has a so called center tip 2 which merges with a tapering drill portion 3 which in turn merges with a cylindrical shaft portion 4. Above said cylindrical shaft portion a collar 5 is provided which is followed by a shaft portion 6, which is adapted to clamp the drill in the drilling head of a drilling machine. It appears from figure 1 in combination with figure 2, that adjacent the lower end of the drill, cutting edges 7, in this case two cutting edges, have been formed. In the embodiment shown, said cutting edges have been formed by providing two recesses 8 in the relative drill portion, e.g. by grinding, whereby the sharp cutting edges 8 are generated. Said cutting edges 7 are effective if the drill rotates according to the arrows 9 as shown in the drawing. Figure 3 shows a cross-section of a piece of sheet material 10 in which a hole, having a diameter 11, may be provided by using the drill, the hole diameter corresponding to the diameter of the drill shaft portion 4. When the drill starts operating first the portion 12, to the left in figure 3, is cut away by the cutting edges 7, whereafter the smooth flowdrill portion 3 enters in action and finally the hole is obtained, as shown to the right in figure 3, having an upset collar 13 at the upper end and an extruded sleeve shaped projection 14 at the lower side of the hole. This upset material at both sides of the sheet provides additional material for the provision of screw thread whereby the sheet may be secured to other parts by means of bolts or screws. It will be clear that the cutting edges in the lower shaft portion of the drill may be formed in a manner which differs from that which has been described above. As said, preferably the axial length of the portion having the cutting edges 7 is substantially equal to 1/3 of the diameter of the holes to be made and therefore of the diameter of the shaft portion 4.

Claims: CLAIMS 1. A flowdrill having a shaft with a substantially smooth tapering effective end, characterized in that one or more cutting edges (7) are provided on the effective shaft surface, adjacent to the tip of the tapering portion (2, 3). 2. Flowdrill according to claim 1, characterized in that the cutting edges (7) are formed in the shaft tip (2, 3) by means of recesses (8) having sharp edges (7) which recesses are provided in the tip surface. 3. Flowdrill according to claim 1 or 2, characterized in that the axial length of the shaft portion having the cutting edges (7) has a length which is equal to substantially 1/3 of the hole diameter(11) to be provided.

Inventors: DEKKERS, GERARD JOHAN
Applicants: FLOWDRILL B.V.
Application year: 1984
Main classification: B23B51
IPC codes: B23B51, B21C37