GB2195564A

GB2195564A - Piloted drill tip

Info

Publication number: GB2195564A
Application number: GB8723332A
Authority: GB
Inventors: George Waddell
Original assignee: Individual
Current assignee: Individual
Priority date: 1986-10-11
Filing date: 1987-10-05
Publication date: 1988-04-13
Anticipated expiration: 2007-10-05
Also published as: GB8723332D0; GB8624430D0; GB2195564B

Abstract

The piloted drill tip (14) is located at the leading end of drill bit (10) and which has a diameter less than the drill bit (18) diameter. The tip (14) is securely fastened, usually by brazing, to the leading end of the drill bit. The tip provides better penetration, line holding and spoil removal than with existing drill bits. In one arrangement, the leading end of the drill bit (10) is machined to define a slot (22) into which is inserted a combined-drill tip (16) and piloted tip (14) of reduced diameter, to be inserted and brazed in position. The tips (14, 16) can be separate and coupled by a slotted coupler (30). <IMAGE>

Description

SPECIFICATION Piloted drill tip The present invention relates to a piloted drill bit, particularly, but not exclusively, for use with masonary drills and the like to provide improved penetration rates and improved hole quality and location.

Existing drill bits for drilling holes in masonary materials such as concrete, rock and the like are slow and there is a tendency to stall with larger sizes. Moreover, because the cutting edge is substantially the same diameter as the drill, any contact with a harder material than the material being drilled, such as aggregate or flint causes the drill to deviate resulting in a hole which is not straight. Moreover, with existing drills, hole location can be difficult because of the initial difficulty in obtaining penetration, with the result that chipping can occur at the hole edges and the hole location may not be centered precisely in a desired position. Moreover, existing masonary drill bits having a cutting edge supported substantially on only one side and this means the tip can break when used with hard aggregate materials.Thus, such existing masonary drill bits are generally used for softer materials and are limited in size for use with conventional rotary percussion drilling machines because the hammer action of the drill is generally insufficient to cause acceptable penetration rates in hard materials.

Consequently, existing masonary drill bits tend to be used with hammer drills with a true hammer action which are expensive. Less expensive hammer drills generally do not provide the true hammer action and the rates of penetration obtained using drills of the aforementioned type is generally unsatisfactory.

An improved masonary drill should satisfy a number of desirable criteria in addition to being relatively inexpensive and easy to fabricate. It should provide improved penetration rates substantially greater than with comparable standard drills and it should provide hole quality. The drill should also have less tendency to deviate even when used on materials having aggregates and flints and the like. The drill should permit improved hole location and minimise chipping at the hole edge of the surface drilled.

The drill bit should be based on a flexible design which can be tailored to suit specific materials being drilled to optimise drilling efficiency, the rate of penetration, ease of use and should minimise the tendency of the drill ing machine to stall. The drill bit should also be capable of being used with both hand held drills and with heavy duty type drilling ma chines and should be capable of being used with any hard material in which a high rate of penetration and improved hole quality is de sired.

An object of the present invention is to provide an improved drill which obviates or mitigates the aforesaid disadvantages.

This is achieved by providing a piloted drill tip at the leading end of a drill and which has a diameter less than the drill bit diameter. The piloted drill tip is securely fastened, usually by brazing, to the leading end of the drill bit. The piloted drill tip provides better penetration, line holding and spoil removal than with existing drill bits.

In one arrangement, the leading end of the drill bit is machined to define a slot into which is inserted a drill tip with a piloted leading tip of reduced diameter. Then the piloted leading tip is inserted and brazed in position to create the piloted drill bit. Various designs of the drill tip are disclosed in the following description.

The drill tip has improved support on both sides at its leading end to minimise the risk of tip damage and the tip can be made by modifying conventional drill geometry in order to minimise cost.

Accordingly, in one aspect of the present invention there is provided a piloted drill bit comprising a drill bit of a first diameter having a piloted drill tip at its leading end, said pi loted drill tip being of a smaller diameter than said drill bit diameter.

Preferably, said piloted drill tip has a cutting edge across its diameter, said cutting edge being supported substantially on both sides by said drill bit. Conveniently, said piloted drill tip is proportioned in relation to said drill to facilitate spoil removal.

Preferably, said piloted drill tip is bonded, brazed or welded to said drill. Conveniently, said piloted drill tip is a one-piece generally planar tip having a first portion of a width substantially the same as the diameter of said drill tip, and a second leading tip portion of lesser diameter than said first portion, said second leading tip being coupled to said first portion by respective shoulder portions, said one-piece tip being of a thickness adapted to be received in a slot disposed at the leading end of said drill bit.

Alternatively, said piloted drill tip consists of a first generally planar portion having a width substantially the same as the diameter of a drill bit and a depth adapted to be received in a slot disposed at the leading end of the drill bit, and a second separate piloted tip portion of a lesser width than said first portion and coupling means adapted to couple said first and said second portions together to form a piloted drill tip. Conveniently said coupling means comprises a cylindrical rod having a slot in each planar end face adapted to re ceive said first and said second tip portions.

Alternatively said coupling means may be a two part portion adapted to define recesses for receiving said first and said second cou pling means. Conveniently, said first and sec ond tip portions and said coupling means can be bonded or brazed together to form a com posite piloted drill tip and bonded, brazed or welded together with said drill.

Accordingly, in another aspect of the inven tion there is provided a piloted drill tip com prising a generally planar tip having a first por tion of substantially the same diameter as a drill bit and a second integral leading portion of reduced width, said second leading portion being coupled to said first portion by shoulder means, said tip being adapted to be disposed in a slot or similar recess.

Accordingly, in yet another aspect of the invention there is provided a piloted drill tip comprising a first generally planar portion adapted to be disposed in a slot or similar recess in the leading end of the drill bit, a second separate leading portion of substan tially less diameter than said first portion and adapted to be coupled thereto by coupling means.

Conveniently, said coupling means is a generally elongate member having means for receiving said first and said second portions and for locating said first and said second portions in the leading end of said drill bit.

Conveniently, said coupling means has slots in either end for receiving said first and said sec ond generally planar tip portions. Alternatively, said coupling means has a slot in one end and a through slot for receiving said first and said second portions respectively.

Alternatively, said coupling means may be provided by using split halves,each split half being essentially symmetrical about a common axis to receive said first and said second tip portions to provide a composite piloted drill tip adapted to be disposed in a slot or recess located in the leading end of the drill bit.

Accordingly, in yet another aspect of the invention there is provided a method of mak ing a piloted drill bit said method comprising the steps of providing a drill bit with a leading end adapted to receive a piloted drill tip, providing a piloted drill tip having a first portion of substantially the same width as the drill bit diameter and a second portion of a lesser diameter than said first portion, disposing said piloted drill tip at said drill bit such that said second portion provides the leading piloted tip of the drill, and fastening said piloted drill tip to said drill bit.

Preferably, said piloted drill is fastened to said drill by bonding, brazing or welding. Al ternatively, said piloted drill tip may be bonded to said drill bit by adhesive.

These and other aspects of the invention will become apparent from the following de scription when taken in combination with the accompanying drawings in which: Fig. 1 is a perspective view of part of a drill bit in accordance with an embodiment of the invention depicting a one-piece piloted drill tip disposed at the leading end of the drill bit; Fig. 2 is similar to Fig. 1 and depicts a twopart drill tip adapted to be disposed in a slot in the leading end of the drill bit; Fig. 3 is a similar view of Fig. 2 and depicts a three-part drill tip adapted to be disposed in a recess in the leading end of the drill bit; Figs. 4a and 4d depict alternative types of coupling means used with the tip shown in Fig. 3, and Fig. 5 depicts split halves of coupling means of the type shown in Fig. 4 for use with a two part tip as shown in Fig. 3.

Figs. 6a and b are similar to Figs. 1 and 2 and depict piloted drill bits in accordance with embodiments of the invention used with a hammer drill.

Reference is first made to Fig. 1 of the drawings which depicts parts of a drill bit 10 having a leading portion 12 which terminates in a piloted drill tip generally indicated by reference numeral 14. The drill tip 14 is part of a one-piece tip 16 which is generally planar and which has a portion 18 substantially of the same width as the diameter of the drill bit 10 and which is coupled to leading portion 14 by shoulders 20. In the end of the drill 10 is a machined slot 22, as best seen in Fig. 2, for receiving the one-piece tip 16. The leading portion 12 of the drill bit 10 terminates in nose portions 24 which are adapted to lie opposite the piloted portion 14. Thus the cutting edge 25 of the piloted portion is supported substantially across its width which minimises the likelihood of damage to the cutting tip by virtue of retention of drill cone diameter to support pilot tip.

Portion 16 is disposed in the slot 22 and is secured therein by brazing the portion to the drill bit forming a brazed joint generally indicated by reference numeral 28 in Fig. 1.

In use, the stucture shown in Fig. 1 provides an improved drilling penetration rate than with conventional drills. This is because the piloted drill tip 14 rapidly enters the masonary and spil is conducted rapidly away from the tip becaue of the difference in diameter between the tip and the drill bit. Also, the piloted tip provides a much less tendency to deviate due to contact at differing levels along bit with aggregates or flint and this results in improved hole quality which are generally truer and straighter. Also, drill positioning is easier and there is ma much less tendency for a hole to be chipped at the edge of the surface drilled.

As best seen in Fig. 2 the one-piece tip 16 can be replaced by two separate pieces and bonded, brazed or welded in the manner aforedescribed. The choice of tip would depend on the ease and cost of manufacturing the separate tip, otherwise the structure shown in Fig. 2 is the same as for Fig. 1. In this arrangement the use of two separate pieces provides a drill bit with torsional resilience which assists in minimising tip wear and the risk of tip damage.

Reference is now made to Fig. 3 of the drawings which depicts a further embodiment in accordance with the invention. In this embodiment, the tip 16 consists of a leading piloted tip portion 14 and a trailing portion 18 and a coupling member 30 in the form of a cylindrical rod or other suitable external form having slots 32 and 34 at each end thereof.

The slots are proportioned to receive tip portions 14 and 18 and the assembly is adapted to be disposed in the leading end 12 of the drill bit 10. The leading end 12 has a slot 22 with a cylindrical centre recess adapted to receive the circular or other suitable shape of the coupling member 30. Assembly similar to the structure shown in Fig. 2 in which all components are disposed together and then brazed to form a structure substantially as shown in Fig. 1.

With the structure shown in Fig. 3 the cylindrical coupling member 30 permits some torsional resilience of the piloted drill bit which assists in minimising tip wear and the risk of tip damage.

As best seen in Fig. 4 of the drawings, the coupling member 30 may be replaced by a different member, examples of which are shown in Figs. 4a, 4b, 4c and 4d. The member as shown in Fig. 4b consists of an end slot and a through slot and that in Fig. 4c has a single slot which is narrow at the end and which widens towards the centre of the member. Also, Fig. 4 illustrates a coupling member 30 with a single slot disposed on one end only and is proportioned to receive tip portions 18 and 14. Alternatively, the coupling member 30 may be configured using split halves 36 and best seen in Figs. 5a, b and c.

Two symmetrical halves are disposed together and the tip portion inserted accordingly in the slot or slots defined by both halves. Both halves when joined together will provide a structure similar to those shown in Fig. 4. An advantage of this arrangement is that greater flexibility in manufacturing is achieved.

It will be appreciated that various modifications may be made to the embodiments hereinbefore described without departing from the scope of the invention. For example, the design can be tailored to specific materials so that the reduced diameter nose for soft materials could be 70% of the desired hole diameter and for hard materials would be 30% to 50% of the desired hole diameter. For holes to be drilled deep, the reduced diameter nose can be extended to ensure that aggregate or flint can be penetrated prior to the main tip encountering the same chip. The piloted drill bit can be applied to various types of drills including masonary drills and hammer drill types as shown in Fig. 1 to 6. The drill tip can be of any suitable material sufficient to drill through masonary and the like.Also, multiple stepped tips may be provided to the drill bit as shown in Fig. 7 which may be suitable for use with large drills of about 40mm diameter.

Advantages of embodiments described are that the drill with a piloted drill tip has penetration rates substantially greater than with existing standard drills and hole quality is much improved with the holes drilled with the piloted drill tip being much truer and straighter because the piloted drill tip has a much less tendency to deviate during drilling due to contact with aggregates, flint and the like. The piloted drill bit shown in Figs. 1,2,3,6b and 7 have improved torsional resilience which assists in minimising tip wear and the risk of tip damage. The piloted drill tip permits a greatly improved hole location because the drill holds position and greatly reduces chipping at the hole edge on the drilled surface. Furthermore, the design can be tailored to specific materials and for drilling deep holes the reduced diameter nose can be extended to ensure that aggregate is penetrated prior to the main tip encountering the same chip. The provision of a smaller pilot tip followed by a larger tip permits a space for spoil to flow through and rapid removal of spoil facilitates the rate of penetration.

Claims

1. A piloted drill bit comprising a drill bit of a first diameter having a piloted drill tip at its leading end, said piloted drill tip being of a smaller diameter than said drill bit diameter.

2. A piloted drill bit tip as claimed in claim 1 wherein said piloted drill tip has a cutting edge across its diameter, said cutting edge being supported substantially on both sides by said drill bit.

3. A piloted drill bit tip as claimed in claim 1 or claim 2 wherein said piloted drill tip is proportioned in relation to said drill to facilitate spoil removal.

4. A piloted drill bit tip as claimed in any preceding claim wherein said piloted drill tip is a one-piece generally planar tip having a first portion of a width substantially the same as the diameter of said drill tip, and a second leading tip portion of lesser diameter than said first portion, said second leading tip being coupled to said first portion by respective shoulder portions, said one-piece tip being of a thickness adapted to be received in a slot disposed at the leading end of said drill bit.

5. A piloted drill tip bit as claimed in any one of claims 1 to 3 wherein said piloted drill tip consists of a first generally planar portion having a width substantially the same as the diameter of a drill bit and a depth adapted to be received in a slot disposed at the leading end of the drill bit, and a second separate piloted tip portion of a lesser width than said first portion and coupling means adapted to couple said first and said second portions together to form a piloted drill tip.

6. A piloted drill bit tip as claimed in claim 5 wherein said coupling means comprises a cylindrical rod having a slot in each planar end face adapted to receive said first and said second tip portions.

7. A piloted drill bit tip as claimed in claim 5 wherein said coupling means may be a two part portion adapted to define recesses for receiving said first and said second coupling means.

8. A piloted drill bit tip as claimed in any one of claims 5 to 7 wherein said first and second tip portions and said coupling means can be bonded or brazed together to form a composite piloted drill tip and bonded, brazed or welded together with said drill.

9. A piloted drill bit tip as claimed in any one of claims 5 to 7 wherein a piloted drill tip comprising a generally planar tip having a first portion of substantially the same diameter as a drill bit and a second integral leading portion of reduced width, said second leading portion being coupled to said first portion by shoulder means, said tip being adapted to be disposed in a slot or similar recess.

10. a piloted drill bit tip as claimed in any one of claims 5 to 7 wherein a piloted drill tip comprising a first generally planar portion adapted to be disposed in a slot or similar recess in the leading end of the drill bit, a second separate leading portion of substantially less diameter than said first portion and adapted to be coupled thereto by coupling means.

11. A piloted drill tip as claimed in claim 10 wherein said coupling means is a generally elongate member having means for receiving said first and said second portions and for locating said first and said second portions in the leading end of said drill bit.

12. A piloted drill tip as claimed in claim 11 wherein said coupling means has slots in either end for receiving said first and said second generally planar tip portions.

13. A piloted drill tip as claimed in claim 11 wherein said -coupling means has a slot in one end and a through slot for receiving said first and said second portions respectively.

1-4. A piloted drill tip as claimed in claim 11 wherein said coupling means may be provided by using split halves, each split half being essentially symmetrical about a common axis to receive said first and said second tip portions to provide a composite piloted drill tip adapted to be disposed in a slot or recess located in the leading end of the drill bit.

15. A method of making a piloted drill bit, said method comprising the steps of providing a drill bit with a leading end adapted to receive a piloted drill tip, providing a piloted drill tip having a first portion of substantially the same width as the drill than said first portion, disposing said piloted drill tip at said drill bit such that said second portion provides the leading piloted tip of the drill, and fastening said piloted drill tip to said drill bit.

16. A method as claimed in claim 15 wherein said piloted drill is fastened to said drill by bonding, brazing or welding.

17. A method as claimed in claim 15 wherein said piloted drill tip may be bonded to said drill bit by adhesive.

18. A piloted drill tip substantially as hereinbefore described with reference to Fig. 1 or Fig. 2 or Fig. 3 or Fig. 4 or Fig. 5 or Fig. 6 or Fig. 7 of the accompanying drawings.

19. A method of making a piloted drill tip substantially as hereinbefore described.