GB2312386A

GB2312386A - Raking bit

Info

Publication number: GB2312386A
Application number: GB9617073A
Authority: GB
Inventors: Jon Henry Dobson
Original assignee: Individual
Current assignee: Individual
Priority date: 1996-04-25
Filing date: 1996-08-14
Publication date: 1997-10-29
Anticipated expiration: 2016-08-14
Also published as: GB2312386B; GB9608480D0; GB9617073D0

Abstract

An attachment for a rotary drive tool such as an angle grinder or a drill is provided in the form of an elongate bit adapted at one end 1 to be attached to the drive tool. The other end forms a raking portion 3 and is provided with a cutting surface provided by a diamond coating 4.

Description

RAKING BIT The present invention relates to raking or chasing apparatus particularly, but not exclusively, for removing cement or mortar from between courses of bricks and between bricks within a course or for chasing conduits in walls, etc to receive electric cables and the like.

In construction work and particularly in renovation work, there is a need to remove existing mortar from inbetween the bricks of a building e.g. before pointing.

For small jobs, the mortar can be chipped away manually using a hammer and chisel, but this is clearly not feasible for large scale operations as it is time consuming and labour intensive.

The tool most commonly used to remove mortar, comprises a rotary disk having a circumferential cutting edge formed by metal bonding. The disk is fitted to, and driven by, a hand-held rotary drive mechanism e.g.

an angle grinder. The edge of the disk is guided along the line of mortar to be removed. As the disk rotates, it cuts out the mortar between the courses of bricks.

One problem with the disk tool is that it can only cut in a single plane. It cannot, for example, cut along a horizontal line then turn to cut a vertical line. When raking mortar between bricks, therefore, the disk is used to rake out the horizontals and the verticals then need to be raked separately, using e.g. a chisel.

Another problem is that the rotating disk can cause chipping of the bricks as it rotates. This is particularly problematical in heritage work where the contractors are bound by contract not to chip any stone.

The disk, having a relatively large surface area, is also inefficient in raking out mortar at corners, between two faces of a building. As the disk is guided round the corner it leaves a radius.

Another disadvantage of the cutting disk is that it is relatively large and heavy and expensive to manufacture.

The cutting disk also creates a great deal of dust.

The present invention aims to overcome the problems of the disk tool.

Also in building work, it is often necessary to form conduits in brick walls etc. within which electric cables and the like are embedded. This 'chasing' is normally carried out by hand, using a chisel to dig out the brick etc, and form a conduit of the desired depth and diameter. This method is, however, extremely time consuming and labour intensive. It is also difficult to produce a uniform conduit of accurate dimensions.

Another chasing method, which is slightly faster and more accurate, involves using a tool with a rotary cutting disk to cut two lines along the wall, defining the width of the conduit to be formed. The brick, etc between the lines is then dug out normally, using a chisel. However, this process is still very time consuming. In addition, as discussed above, the use of a cutting disk creates a large amount of dust and carries the risk of damaging the brickwork. Also, as with mortar raking discussed above, cutting disks cannot be used continuously to cut horizontally and vertically and do not cut around corners in a precise manner.

The present invention also aims to overcome the problems existing in chasing methods.

According to one aspect of the present invention, there is provided a raking bit comprising a fastening portion for attachment to a rotary drive mechanism and an elongate raking portion, said raking portion having a diamond coating.

The bit can be driven by any type of rotary mechanism, although standard rotary tools, which are readily available, such as angle grinders, are preferred.

Thus, in accordance with another aspect, the present invention provides an attachment for an angle grinder, comprising an elongate mortar raking or chasing portion having a diamond coating.

In accordance with a third aspect of the invention, there is provided a mortar raking or chasing tool comprising an angle grinder and a mortar raking or chasing bit to be attached to and rotated by said angle grinder, said mortar raking or chasing bit comprising an elongate cutting part having a diamond coating.

The raking bit is preferably formed as a single component having one end adapted to be attached to an angle grinder, or a drill preferably by means of a screw thread, or SDS fitting, the other end forming the elongate raking portion.

The cutting surface of the raking portion is preferably formed by a diamond grit coating which is preferably formed on the raking portion by electroplating. The use of diamond, usually mixed with nickel, forms an extremely hard and durable cutting surface which is effective in cutting mortar and cement and stone.

It is preferable to use an electroplated coating of diamond with a particularly hard grade of nickel. The harder nickel increases the life of the tool and is particularly suitable for cutting into cement which contains highly abrasive sand. A grit size of 25/30 is presently preferred.

In one embodiment, the raking bit comprises a hollow cylindrical fastening portion of circular crosssection, with an inner thread. This portion is dimensioned to fit a standard angle grinder. One end of this portion then tapers inwards and continues as a narrower, elongate, cylindrical raking portion with a rounded end, which is completely coated in diamond grit.

The diameter of the raking portion may, of course, be made to any size, but preferably corresponds to standard widths between bricks and courses of bricks.

It is envisaged that bits with raking portions of 4mm, 6mm, 8mm, 10mm and 12mm diameter will be supplied. The length of the raking portion can, again, be made to any size, but will preferably correspond to the maximum permissible raking depth of 25mm.

The fastening portion is preferably provided with at least two flattened portions to enable it to be securely gripped by a spanner for fastening and unfastening.

In a second embodiment the raking portion has a pointed end, i.e. the end of a raking portion is conical, forming a point which, in use, is pushed into the wall to the desired depth and the tool is then guided along the wall to form the desired conduit.

To prevent the tool jamming and to remove dust, dust flutes may be provided in the form of one or more grooves in the tapering faces of the raking portion.

The invention thus provides a mortar raking or chasing bit which can cut in all directions. For mortar raking, the operator can easily and quickly guide the tool along a course of bricks and between bricks in a course, raking out mortar wherever desired. The bit can rake out mortar from small joints and from corners in a single operation and is not limited to a single plane of movement.

For chasing conduits in walls etc, the operator can easily and quickly guide the tool into the wall and bed back into the wall to form a conduit of the desired dimensions.

Because the raking bit is much smaller than the cutting disk, it reduces the danger of chipping the bricks. This is particularly important in heritage work.

Because the bit can be easily guided where the mortar or brick needs removing, it enables the job to be done more quickly and easily, increasing work efficiency.

Also, since the bit is elongate and rotates into the mortar or brick it produces much less dust than the cutting disk.

Further, the bit of the present invention, in contrast to known cutting disks, is a small, light and simple component which will be far less expensive than the disk whilst having an equally long, or even longer, life. The saving in cost is even greater when a number of different sized cutting tools are needed for different types of brickwork.

A further advantage of the present invention, in its preferred embodiment, is that it is adapted to fit to a standard angle grinder or the like and so new and expensive drive tools are not necessary.

Because the raking bit is so small and light, and is preferably driven by an angle grinder or similar hand tool, it results in a tool which is much easier and more comfortable to use.

Preferred embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings.

Fig. 1 is a perspective view of a mortar raking bit according to one embodiment of the present invention; and Fig. 2 shows a cross-section of the bit of Fig. 1; Fig. 3 is a cross-section of a chasing bit according to a second embodiment of the invention.

The raking bit shown in the drawings is made of a hard metal e.g. EN3B, or EN8. But can be made of any other metal. In the embodiment of Fig. 1, one end of the bit, which forms the part to be attached to the rotary driver, is a hollow cylindrical part 1 of circular cross-section. The diameter of this part is such that it corresponds to the drive spindle of a standard angle grinder. In the preferred embodiment, the outer radius of this part is 19mm.

Alternatively, the shaft may be a plain, cylindrical shaft or be formed with a standard SDS fitting or may have a hexagonal cross-section to fit other standard rotary tools such as drills.

In the embodiment shown in Figs. 1 and 2, a thread is formed as the inner surface of the cylindrical part 1, again corresponding to the outer thread of the angle grinder drive spindle, e.g. a standard M14 thread. The outer end of the cylinder is chamfered 7 at e.g. 45 , to form a lead-in to ensure easy, quick, location of the bit onto the angle grinder.

The length of the cylindrical part 1, in the preferred embodiment, is 34mm.

The bit then tapers inwards at a transitional portion 2 and then continues, at a reduced diameter, to form the elongate raking portion 3. This portion 3 has a circular cross-section and is intended to be supplied in a range of diameters corresponding to standard widths between bricks e.g. 4mm, 6mm, 8mm, lOmm and 12mm although other sizes could, of course, be manufactured.

The length of the raking portion 3 is, in the preferred embodiment, 30mm, to enable it to rake out the maximum depth of 23mm. Of course, other lengths may be used, for example a 175mm (5") version is being considered.

For motar raking applications, the end of the raking portion 3 is rounded, e.g. with a radius of curvature of 8mm, to maximise the raking efficiency.

The diamond/nickle coating 4, preferably with a grit size of 25/30 and incorporating a hard grade nickle, is formed, using any known electroplating technique, along substantially the whole length of the raking portion 3 and over its rounded end, to form a very hard, durable cutting surface.

To enable the bit to be easily unfastened from, and tightly fastened to, the angle grinder, the cylindrical fastening part 1 may be provided on its outer surface with two or more flattened areas 5 adapted to be engaged by a standard spanner. In the preferred embodiment, the bit has two opposed flattened areas 5 formed on the cylindrical fastening part 1, adjacent the transitional portion 2.

In use, the bit, selected to have a diameter appropriate to the job in hand, is fastened to the drive shaft of the angle grinder by means of the matching screw threads 6, using a spanner, engaging the flattened portions, to ensure it is tightly fastened.

The rounded end of the raking portion 3 is engaged in the joint to be raked and the angle grinder is activated. The angle grinder causes the attached bit to rotate and, as it rotates the hard diamond cutting surface routs out the mortar.

The operator guides the tool along the joints to be raked and the bit may be guided in any direction, continuing to cut and rake out the mortar as it is moved.

The bit can be removed from the angle grinder when the job is completed, or to substitute a new or different sized bit by unscrewing, again using a spanner engaging the flattened portions.

In a second preferred embodiment, the tool is adapted for chasing conduits in walls etc. to receive electric cables and the like.

Referring to Fig. 3, the end of the bit to be attached to the rotary driver is shown having a known SDS fitting, having two opposing elongate grooves 9 cut into the cylindrical shaft 8. Instead, the shaft 8 may be a plain cylindrical shaft or may have a hexagonal cross section, and is preferably adapted to be received in a rotary tool such as an electric hand drill.

Although different diameters may be used, an example of a standard diameter for this portion is lOmm.

Break corners 10 may be provided at the attaching end of the shaft 8 to improve and simplify locating of the tool in the drive tool.

At the other end, the shaft tapers out to form a blend radius 11 going into the raking portion 12. The raking portion is formed as a wider cylindrical portion 12a of radius e.g. 15mm, 25mm or 34mm or any other suitable size. This then tapers to a point 12b at an angle of, say, 30". Dust flutes are provided by forming grooves in the tapering surfaces. The raking portion is diamond coated 13 as described above.

This second embodiment is particularly useful for chasing, to provide conduits or channels for electric cables and the like. The bit is fitted to the rotary drive tool and the point is placed against the wall at the point where the conduit is to be formed. The bit is then rotated by the drive tool such that the point cuts into the wall and the point is driven into the wall to the desired depth. The diameter of the cylindrical portion of the raking portion is selected to correspond to the desired diameter of the resulting conduit. The bit is then guided up, down or along the wall with the raking portion rotating to cut out a channel of the required dimensions. Electric cables etc. can then be embedded into the wall and concealed.

Whilst the present invention is mainly for use in raking bricks or mortar, it may be used for other cutting or routing applications e.g. for cutting fibreglass.

Claims

1. A raking attachment in the form of an elongate bit comprising a fastening portion for attachment to a rotary drive mechanism and a raking portion, said raking portion having a diamond coating.

2. An attachment for an angle grinder comprising an elongate bit having a mortar raking portion provided with a diamond cutting surface.

3. An attachment as claimed in claim 1 or 2, wherein said raking portion is an elongate cylindrical portion having a rounded end, wherein substantially the entire raking portion, including the rounded end, is coated in diamond grit.

4. An attachment as claimed in claim 1 or 2, wherein said raking portion is in the form of a cylindrical cone, having a pointed cutting end, at least the cutting end being substantially coated in diamond grit.

5. An attachment as claimed in any preceding claim, wherein the bit is provided with a hollow cylindrical portion provided with an inner thread adapted to engage with an outer thread of a drive shaft of an angle grinder.

6. An attachment as claimed in claim 1, wherein the fastening portion is in the form of a cylindrical shaft adapted to fit into a drill chuck.

7. An attachment as claimed in any preceding claim, further comprising dust flutes in the form of one or more grooves in the raking portion.

8. A mortar raking or chasing tool comprising a rotary drive tool and a mortar raking or chasing bit to be attached to and rotated by said rotary drive tool, said mortar raking or chasing bit comprising a cutting end portion having a diamond coating.

9. An attachment or tool substantially as hereinbefore described as shown in the accompanying drawings