Saw blades such for example as hacksaw blades and bandsaw blades, are usually made from a bi-metal strip comprising a cutting edge of high speed steel attached to a support strip. Cutting teeth are cut into the blade edge, typically by electron beam butt welding. The support strip may be a high carbon steel support strip.

Saw blades such for example as hacksaw blades and bandsaw blades are also made by attaching at least one abrasive material to a support strip. The abrasive material may be attached by, for example, brazing, welding or fusing.

The abrasive material may be tungsten grit, diamond powder, or a sintered material such for example as a sintered ceramic material. Because of the abrasive material, the cutting edge of the saw blades does not have conventional or regularly spaced teeth such as would be the case with a saw blade having a high speed steel edging. This lack of conventional or regularly spaced teeth may be disadvantageous in certain applications.

Toothed saw blades employing pre-formed tungsten teeth individually attached by brazing to the edge of a support strip have been made. However, their manufacture is costly and slow. Also, it is difficult to make a saw blade with more than some ten teeth per inch.

Additionally, each facet of the tooth is ground individually from a cylinder or sphere of tungsten carbide. This is a complicated and time consuming process.

It is an aim of the present invention to provide an improved method of making a saw blade.

Accordingly, in one non-limiting embodiment of the present invention there is provided a method of making a saw blade, which method comprises forming at least one recess along an edge of a support strip, and securing in the recess at least one material providing, or enabling the provision of, a sawing edge.

The recess may be formed in the edge of the support strip by rolling.

The recess may be one of a number of shapes. Thus, for example, the recess may be V-shaped, U-shaped, or part circular in section.

A plurality of individual saw teeth may be inserted into the recess to provide the cutting edge. The individual saw teeth may be made of diamond, tungsten carbide, a sintered metal, a sintered ceramic material, or mixtures of these materials.

Alternatively, the recess may be formed with tungsten powder, subsequently compressed and sintered to form a hardened edge to the support strip, into which edge saw teeth may be cut or ground. The sintering and the tooth cutting may be achieved by means of at least one of a laser beam, diamond grinding and wire erosion.

The recess may alternatively be filled with a mixture of tungsten grit and braze material, which may be subsequently heated to form a hardened edge into which saw teeth may be cut or ground.

Alternatively, the recess in the support strip may be provided along its length with a plurality of shorter lengths of tungsten carbide strip, separated one from another. The lengths of tungsten carbide strip may be attached to the support strip by means of brazing, welding, or fusing. The lengths of tungsten carbide strip may have teeth formed in them prior to assembly with the support strip, or the length of tungsten carbide strip may have teeth cut in the lengths after assembly with the support strip.

In another aspect, the present invention provides a saw blade made by the method of the invention.

The manufacture of the saw blade in accordance with the present invention provides a number of advantages over prior art methods. For example, using the method of the invention, it is possible to manufacture a saw blade with a cutting edge of greater width than that of the support strip.

Also, the use of the support strip with the recessed edge enables the manufacture of a continuous or near-continuous bi-metal saw blade. Such a saw blade may comprise a strip of steel and a cutting edge material. The cutting edge material may be, for example, tungsten, diamond, or a sintered material. The sintered material may be, for example, a ceramic material. The cutting edge material provides, or subsequently has formed in it, the cutting edge.

The use of the recessed edge also enables individual small saw teeth to be quickly and accurately placed on, and affixed to, the steel strip. This enables the saw blade to be provided with a greater number of teeth per inch than was possible with previously known methods of manufacture employing individual attachable saw teeth. Following the placing and attachment of the individual saw teeth in the recess formed in the support strip, the recess may be mechanically closed upon the teeth, thereby giving an additional mechanical grip upon the individual teeth.

The recessed edge also enables pre-sintered carbide powder intended to form the saw blade edge to be pressed into position in the recess prior to curing. The curing may typically be means of a laser, electron beam energy, or induction techniques.

Embodiments of the invention will now be described solely by way of example and with reference to the accompanying drawings in which:- Figures 1-5 show different stages in the manufacture of a saw blade by a method of the invention.

Referring to Figure 1, there is shown an end view of a support strip 2 which is made of rolled steel. A recess 4 is provided along an upper edge 6 of the support strip 2.

Figure 2 shows how tungsten 8 is provided in the recess 4. The tungsten 8 may be in powder form and it is brazed into position in the recess 4.

Figure 3 shows how edges 10,12 have been ground to leave material for a cutting edge, also known as a saw kerf.

Figure 4 is a perspective view of the support strip 2 as shown in end view in Figure 3.

Figure 5 shows how the support strip 2 shown in Figure 4 is then provided with teeth 14. The teeth 14 can be provided by laser cutting and/or grinding.

Figures 6-14 show different stages in the manufacture and milling operation of a saw blade according to an embodiment of the invention.

Figure 6 shows a side sectioned view tooth mounted in a recess before the milling operation.

Figure 7 is a base view of the saw tooth of Figure 6.

Figure 8 is a top view of the saw tooth of Figure 6.

Figure 9 is a side sectioned view of the saw tooth of Figures 6-8 after being processed by a first grinding operation.

Figure 10 is a base view of the saw tooth of Figure 9.

Figure 11 is a top view of the saw tooth of Figure 9.

Figure 12 is a side sectioned view of the saw tooth of Figures 6-11 after being processed by a second grinding operation.

Figure 13 is a base view of the saw tooth of Figure 12.

Figure 14 is a top view of the saw tooth of Figure 13.

Referring to Figures 6-14 a method of forming finished saw teeth is shown in three stages. Figures 6-8 show a saw tooth"blank"16 inserted into the pre-pressed recess 4. This"blank"16 is placed in the recess at an angle of substantially 30° to the horizontal line of the recess 4 although the angle may be varied according to requirements.

The tapered shape of the saw tooth 16 produces a facet or cutting angle whereby the wider portion is placed pointing forward to produce the tip of the tooth.

Figures 9-11 show the saw tooth 16 after a first milling operation which cuts the front of the tooth 16 and the top of an adjacent tooth (not shown).

This produces cutting angles on the top surface of the blade and the sides thereof.

After this grinding operation at the top and back of the tooth 16, the portion of the tooth at the base 18 of the grind is narrower than the tip 20.

This is because the tooth 16 was placed at an angle to the grind. Thus at this stage of the milling operation four facets have been created, top, back and two side facets or cutting angles.

The next grinding operation, processes the sides of the teeth 16, removing excess carbide not used for cutting. This is a simple grinding operation along the whole sides of the blade, processing all the individual saw teeth 16.

The result of these grinding processes is a complex multifacted tooth.

Previously this was only achieved by individual grinding of facets.

The teeth 16 of the present invention are advantageously created as the result of the position, shape and angle of the carbide insert and by"gang" milling, i. e. multiple milling in one operation, of the carbide. This process cuts many teeth in one operation and produces at least four facets.

It is to be appreciated that the embodiments of the invention described above with reference to the accompanying drawings has been given by way of example only and that modifications may be effected. Thus, for example, material other than rolled steel for the support strip 2 may be employed. The recess 4 may be other than the illustrated V-shape so that, for example, the recess 4 may be U-shaped. The material used for forming the teeth 14 may be other than tungsten. A saw set may be induced by local bending and the support strip 2 may be regarded as being a backing strip.