GB2185915A

GB2185915A - Drilling and thread forming fastener

Info

Publication number: GB2185915A
Application number: GB08700157A
Authority: GB
Inventors: George Jesson
Original assignee: USM Corp
Current assignee: USM Corp
Priority date: 1986-01-09
Filing date: 1987-01-06
Publication date: 1987-08-05
Also published as: IT1215326B; GB2185915B; IT8719016A0; FR2592693A1; JPS62242111A; DE3700499C2; FR2592693B1; AU6716087A; AU586060B2; GB8700157D0; CH672171A5; CA1285798C; DE3700499A1

Abstract

The fastener has a threaded shank and a pilot end 16. A pair of cutting surfaces is provided by flutes and is provided on the pilot end, each surface terminating in a cutting edge 26, 28. A linear groove 38, 40, arcuate in cross-section, is disposed adjacent the respective cutting edge 26,28 in the cutting surface. The surfaces and grooves are formed by mating dies 50 with complementary surfaces 52, 56. <IMAGE>

Description

SPECIFICATION Groove point screw The present invention relates to a rotarythreaded fastener of the self-drilling and threading type and more particularyto a fastener which is manufactured by a pair offorging dies.

Self-drilling and thread forming fasteners are well known in the art. Some of these fasteners are particularly adapted for manufacture by a milling process, others for manufacture by a forging process which employs a pair of matched dies, and some are capable of manufacture by either process. Atypical exampleofatypeofdrillingandthreadforming fastener which is preferably formed by the forging process is described in U.K. Patent 1,195,246 (U.S.

Patent 3,395,603). Fasteners manufactured in accordance with the teachings of the above patent have met with wide acceptance as they provide a fastener which is simple to use, requiring no pre-drilling ofthe structuretowhich it is assembled, and these fasteners have proven to be easy to manufacture by mass production techniques.

As the use of these self-drilling and thread forming fasteners hasincreased,the requirementforthe reduction in drilling time of the fastener has become important, particularly in those instances such as automobile manufacture, metal building construction, etc. where a large number of these fasteners are employed, and in particular, where mass production lines are employedto produce the product. In developing an improved threaded fastener of the self-drilling and threaded type, therefore, a decrease in drilling time has become an ever important factor in the design.

It is therefore an object of the present invention to provide a drilling and thread forming fastener which exhibits a decrease in drilling time over hitherto known drilling and thread forming fasteners.

It is a further object of the present invention to provide a drilling and thread forming fastener wherein the fastener exhibits an improvement in drilling time, particularly in the initial stages of the drilling. According to the present invention we provide a drilling and thread forming fastener comprising a threaded shank and a pilot end having a pair of transverse axes intersecting at the centerline of said fastener, a pair of flutes extending longitudinally over said pilot end to form a pair of cutting surfaces, in cross section defining one of said axes and terminating in a cutting edge, said flutes further forming a pair of lands concentric with the centerline of said shank, each land having an arcuate surface extending outwardly to define the other of said axes at its radial extent on any cross-section of said pilot end, and a linear groove arcuate in cross-section formed in each said cutting surface adjacent to said cutting edge.

Preferably, the drilling and thread forming fastener may be provided with an axis defined by the cutting surface which is of a greater magnitudethan the axis defined bythe arcuate surfacesofthe lands A drilling and thread forming fastener may also be provided wherein the groove extends over the entire length ofthe cutting edge.

A pair of mating diesforformingthepilotendofa drilling fastenertherebetween in a cold forging process is provided wherein each mating die comprises a portion disposed forforming a cutting surface on a workpiece by forcing the dies together against the workpiece during the forging process, the surfaces terminating at a mating surface ofthe dies a protruding portion arcuate in cross-section extends from the cutting surface forming portion adjacent the mating surfaceforforming a groove in the fastener cutting surface, during the cold forging process.

A preferred embodimentofthe invention will now be described by way of example with reference to the accompanying drawings in which:~ Fig. is a fragmentary elevational view of a drilling and thread forming fastener according to the present invention; Fig. 2 is an elevational view showing the fastener of Fig. 1 rotated through 90 ; Fig. 3 is an end view taken on an enlarged scale, showing further details of the fastener depicted in Figs. 1 and 2; Fig. 4 is a prospective view showing an end portion of the fastener of Figs. 1 and 2 in detail; Fig. 5 is an enlarged sectional viewtaken along the lineV-VofFig. in detail;; Fig. 6 is a schematic view showing a priorart fastener du ring application; Fig. 7 is a schematic view similarto Fig. 6 showing the fastener of Figs. 1 and 2 during application; and Fig. 8 is an elevational perspective view showing one of a pair of mating dies employed in forming the fastener of Figs. 1 and 2.

Referring nowto the drawing and in particular to Figures 1-4, there is shown a drilling and thread forming fastener 10 having a shank 12 on which a continuous thread 14 is formed, and a pilot end 16. The fastener 10 is substantially symmetrical about the centerline of the shank 12, however, having a transverse major axis x-x and a transverse minor axis y-y intersecting atthe centerline ofthe pilot end 16. A pair offlutes 18 and 2Careformed in the pilot end 16 and extend longitudinally over the length of the pilot end to form a pair of cutting surfaces 22,24 extending along the major axis and in general defining the extent of the major axis ofthe fastener at any section thereof.

Each of the cutting surfaces 22 and 24 terminates in a cutting edge 26,28 which forms an acute angle with the centerline ofthefastener 10. The cutting edge 26, 28 is disposed for preliminary entry into the metal surfaceto provide a lead forthe pilot end 16 ofthe fastener.

Each oftheflutes 18,20 further serves to define a pair of lands 30,32 which are concentric with the centerline ofthe shank 12. The lands each have an arcuate surface34,36 projecting outwardly to define the minor axis at its radial extent on any cross-section ofthepilotend 16.

As shown in Figures 1-4, the fastener 10 is provided with a pairof lineargrooves 38,40formed in the cutting surface 22 or 24 adjacent the cutting edge 26 or 28 respectively. In the embodiment shown, the linear groove 38,40 extends overthe entire length ofthe respective cutting edge 26 or 28.

Referring to Figure 5, the groove 38 is shown to be arcuate in cross-section and is not restricted to being a true circular arc. The effect ofthe lineargroove 38 or40 isto produce a continuous chip, as best shown in Figure 7 ratherthan a plurality ofsmall chip segments, which are produced by fasteners of the prior art (shown in Figure 6), thereby providing a chip which willflowsmoothlythrough theflute 18 or20 and from the hole being drilled by the fastener.

In forming the groove 38, in orderto maintain the integrity ofthefastener it has been found thatthe groove depth Dshould be approximately from 15 percent to 40 percent of the web thickness W, as shown in Figure 3.

Referring nowto Figure 8,there is shown a die 50 which is one of a pair of mating dies employed to producethefasteners shown in Figures 1-4. The die 50 is similar to that shown in U.K. Patent 1,195,246, but incorporatestheimprovementto provide a fastener described with references to Figures 1-7.

The die 50 comprises a portion 52 disposed for forming the cutting surface 22 on a workpiece and related surfaceforforming the pilot end 16 ofthe fastener in a forging process, which is well-known in the art.

In order to accomplish the objective ofthe present invention, the surface 52, and its similar surface on the mating die is provided with a protruding portion 54 arcuate in cross-section, which extends from the cuttingsurfaceforming portion 52 and is effective to produce the linear groove 38 when the pilot end is formedinafastenerduringthecoldforging process.

In the embodiment shown, the surface 52 terminates at a mating surface ofthe die cooperating with the die 50 at a linear portion 56 and the protruding portion 54 extends along the line ofthe mating surface in orderto produce the groove 38 (our groove40) in the fastener 10 described with reference to Figures 1-4.

It has been found with the structure hereinbefore described thatthe linear groove 38 or40 provided in thecuttingsurface 22 or 24 ofthe pilot end 16 is effective to produce a planing action due to the low lip relief angle, and thereby exhibits improved performance offastener drilling time. The cutting surface 22 or 24 having the linear groove 38 or40 respectively formed therein creates a scooping action at the extremity of the drill tip # ti p which is extremely effective in the initial stage of drilling.

As further described with reference to Figures 6 and 7,the linear groove 38,40 formed in the cutting surface 22 or 24, respectively, produces a continuous chip which serves as a mechanism for drawing the point through the material being drilled, thereby exhibiting improved performance and fastener drill ing times.

Claims

1.- A drilling and th read forming fastener compris- ing athreaded shank and a pilot end having a pair of transverse axes intersecting at the centerline of said fastener, a pairofflutes extending longitudinally over said pilot end to form a pair of cutting surfaces, in cross-section defining one of said axes and terminating in a cutting edge, said flutes fu rtherforming a pair of lands concentricwith the centerline of said shank, each land having an arcuate surface extending outwardlyto define the other of said axes at its radial extent on any cross-section of said pilot end, and a linear groove arcuate in cross-section formed in each said cutting surface adjacent to said cutting edge.

2. A drilling and thread forming fastener according to claim 1, wherein said axis defined by said cutting surfaces is of a greater magnitude than said axis defined by said arcuate surfaces of said lands.

3. A drilling and thread forming fastener according to claim 1 or 2, wherein said groove extends overthe entire length of said cutting edge.

4. A drilling and thread forming fastener according to any one of claims 1 to 3, wherein each said cutting edge is disposed at an acute angle with said centerline.

5. A drilling and thread forming fastener according to any one of claims 1 to 4, wherein said groove extends overthe entire length of said cutting edge.

6. A drilling and thread forming fastener according to any one of the preceding claims, wherein said axis defined by said cutting surfaces is of a greater magnitude than said axis defined by said arcuate surfaces of said lands.

7. A pairof mating diesforforming a pilot end of a drilling fastenertherebetween in a cold forging process wherein each said mating die comprises a portion disposed forforming a cutting surface on a workpiece by forcing said dies together against the workpiece during the forging process, said surface terminating at a mating surface of said dies and a protruding portion, arcuate in cross-section, extend ingfrom said cutting surface forming portion adjacent said mating surface,forforming a groove in said fastener cutting surface during the cold forging process.

8. A drilling and thread forming fastener substantially as hereinbefore described with reference to and as illustrated by Figures 1 to 5 of the accompanying drawings.

9. A pair of mating dies for forming a pilot end of a drilling fastenertherebetween substantially as hereinbefore described with reference to and as illustrated by Figure 8 of the accompanying drawings.