GB2169235A - Improvements relating to blade tools - Google Patents

Abstract

A bolstered hand tool is fabricated by forming a spring steel plate 12 to define a handle portion 12C and a blade portion 12A and sintered metal bolsters 14 are resistance welded to opposite sides of the spring steel plate where the handle portion meets the blade portion. The tool is finished by adding wooden handle portions and by grinding and polishing the bolsters. <IMAGE>

Description

SPECIFICATION Improvements relating to blade tools This invention relates to the manufacture of bolstered blade tools, and in particular concerns the manufacture of tools which are in the nature of hand tools and comprise a blade and a handle with a bolster or bolster therebetween. Such blade tools may comprise, for example, spreader knives or filler knives or even table knives, but in any event are tools in which the blade portion is of spring steel.

Typically in the manufacture of such tools, basic blanks are manufactured by various methods the most common of which is drop forging, in which a round bar steel billot is bolstered by drop forging to an approximate pattern followed by blade rolling to provide a substantially flat blade portion, and so that there are bolster portions on opposite sides of the blade portion at one end thereof and the forging includes a handle strip portion. The thus treated portion is now clipped to shape. These blanks are "soft" at this stage but are subsequently pierced, hardened and tempered. They are supplied in this form to hand tool manufacturers. The method results in quite crude products which have variations in thickness, degree of scale, bolster angles, handle and blade shape and temper.There is therefore a need to reduce the cost of the blanks, achieve better standards of repeatability and reduce the costs of fixing and cutting the scales.

Methods for achieving these objects have been proposed and comprise full length forging buttwelding a blade from strip or bevel section to a cold formed handle, electrically upsetting strips to form bolster bulges, and cold pressing followed by blade cross rolling but which methods have not shown themselves to meet the objectives. It is usual in producing the finished tools to apply to each side of the handle strip portion strips of wood or the like, and the blade and bolster portions are ground to final shape to give the tool what is known as the "professional" appearance.Tools which conventionally are manufactured and which are not produced by this process and therefore do not have the professional appearance, comprise essentially a pressing taken from the steel strip defining the blade, one end of the pressing having a tang which is push fitted into for example a turned wooden handle, and a fabricated bolster may be fitted using rivets or the like.

To produce blade tools by the known processes as described is expensive, and furthermore in the case of drop forging the drop forgings tend to vary as to dimension so much so that it is difficult to provide standard handle strips for these tools. Instead, the handles have to be fashioned to each particular forging. Moreover, the finishing work of grinding the blade and bolsters tends to be time consuming and expensive.

The present invention aims at producing professional quality tools by a three part fabrication. In accordance with one aspect of the invention a blade hand tool is produced by pressing the blade and handle strip support section from spring steel strip and by welding bolsters to opposite sides of the pressing intermediate the ends thereof and at the region where the handle strip support meets the blade end and finishing by applying a handle or handle strips and grinding and/or polishing as appropriate, the sequence of finishing being optional, and the extent of finishing being only sufficient as is required.

By using a welding fabrication process the option is allowed for forming the pressing of prehardened and tempered strip, or, from soft material with subsequent heat treatment.

In a particular embodiment the bolsters are of sintered metal, facilitating their manufacture, and preferably the faces of which are applied to the pressing have grooves so that prior to welding contact between bolsters and the pressing is along a series of parallel links, enhancing the welding operation which is preferably resistance welding.

In relation to the finishing operations, the grinding and/or polishing or the like if required can take place before or after application of the handle or handle strips. When applied, the handle strips may be applied by pins, nails, screws or the like.

The welded bolsters with appropriate grinding and/or finishing can be made to have the appearance of being integral with the blade whereby a tool having the professional look, but costing a fraction of the conventional price, results.

Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, wherein: Figure 1 is a perspective view of a drop forging of a type which is used in the manufacture of a professional hand tool being a scraper or filling knife; Figure 2 is an exploded perspective view of the parts which will make up a hand tool produced by the method according to the invention; Figure 3 is a perspective view showing the finished tool according to the present invention; Figures 4, 5, 6 and 7 show in various views, a form of bolster suitable for use in the present invention; and Figures 8, 9 and 10 show an alternative form of bolster.

Referring to the drawings, in Figure 1 is shown a drop forging 10 as it is supplied from the forge to the manufacturer of tools, for the production of a scraper tool or spreading knife of the form illustrated in Figure 3. The forging has a blade portion 10A, a handle portion 10C and a bolster portion 10B. The blade, handle and bolster regions also have to be ground to make the forging suitable for forming into a hand tool. The handle strip support 10C varies in dimension and applied handle strips such as wood strips 20 shown in Figure 3 have to be shaped individually to fit. the wood strips 20 may be applied by nails, screws, pins or the like.

The drop forging 10 not only is expensive, but it does require a considerable amount of finishing to produce the tool, and because the forgings for the same type of tool vary in size in present manufacturing tolerances, it is difficult to provide a stand ard size of handle strip 20 for the tools.

With the present invention however, best explained upon referring to Figure 2, the blade and handle support strip are formed in single pressings 12 from spring steel plate, and so they can be of consistant size, thickness and physical characteristics and in the central region 12B where the said support strip 12C joins the end of the blade 12A are welded preferably by resistance welding to opposite sides of the pressing bolsters 14. Electric arc welding can be used if desired. Finally, the handle strips 20 as shown in Figure 3 are applied by pinning, screws or the like.

If it is necessary when the components illustrated in Figure 2 are assembled, and the bolsters 14 are welded to the pressing 12, the tool may be finished by grinding, polishing or other process, but the extent of finishing which is required will depend upon how accurate the bolsters 14 and pressing 12 are initially produced and the welding flashing which has to be removed. if it is desired that the blade 12A of the tool should taper to zero or very little thickness at the outer blade end, then it would be necessary to grind the blades 12A.

Referring now to Figures 4 to 10, in Figures 4 to 7 is shown in a first embodiment of a particularly suitable bolster for the present invention, whilst Figures 8 to 10 show an alternative form of an equally suitable bolster. Figure 5 is an underneath plan view of the bolster, Figure 4 is an end view looking the in direction of arrows 4. Figure 6 is an end view looking in the direction of arrows 6, and Figure 7 is a side view in the direction of arrow 7.

Each of the bolsters shown in Figures 4 to 7 and 8 to 10 is of sintered metal, and has a base surface which is to be welded to the pressing 12 shown in Figure 2 by resistance welding, and in particular projection resistance welding. The said base surface is in fact defined by a plurality of ridges 30 defining a saw tooth formation as shown in Figures 4 and 6, and surrounding the ridges and free sides is a sharp peripheral edge 32. The bolster shown in Figures 4 to 7 is of a semi-circular shape in cross-section as indicated by reference 34, and an end surface thereof as shown in Figure 7 has a chamfered portion 36.

The bolster shown in Figures 8 to 10 has the same characteristic features as the bolster shown in Figures 4 to 7, except that the dimensions are slightly different, and the sectional shape of the bolster shown in Figure 10 is defined by an arc of a circle 38 and a cord 40 to that circle. Figure 8 is an underneath plan view of the bolster whilst Figures 9 and 10 are views in the direction of arrows 9 and 10 in Figure 8. The reference numerals 30 and 32 in Figures 8 and 10 again indicates the ridges which form the base surface which is applied to the pressing 12 during the welding operation.

The bolsters are of sintered metal, formulated to lend themselves effectively to resistance welding to the pressing 12, and when they are resistance welded the heat generated by the welding operation in fact melts the ribs 30 and the edge 32 ensuring that the bolster at each side of the pressing becomes firmly fused to the pressing. The finishing operation of the tool is as described in relation to the tool as shown in Figure 3.

Because the resistance welding takes place, in the case of the Figures 4 to 10 embodiments, along ridge lines 30 and 32 (hence the description "projection" resistance welding) and the bolsters are of sintered metal, the effect of resistance welding is to increase thee temperature along the edges rapidly causing rapid melting of the bolster ridges and rapid fusing of the bolsters to the pressing takes place.

The bolsters may of course take any suitable shape, and the examples of Figures 4 to 10 have proved to be particularly suitable.

The invention can of course be used for other tools which have a spring steel blade, central bolsters and a handle.

Claims (9)

1. A method of manufacturing a bolstered hand tool wherein a strip steel blank defines a blade portion and a handle portion and to opposite sides thereof are welded bolsters at the region where the blade portion meets the handle portion.

2. The method according to claim 1, wherein the bolsters are of sintered metal.

3. The method according to claim 2, wherein the bolster surfaces which are applied to the spring steel to be welded thereto are defined by ridges.

4. A method according to claim 3, wherein the bolsters each comprise a body having a surface for application to the spring steel and opposite such surface is a curved surface.

5. The method according to claim 2, 3 or 4, wherein the bolsters are connected to the spring steel by resistance welding.

6. The method according to any preceding claim wherein the bolsters and blade portion are finished by suitable working such as grinding or polishing.

7. The method according to any preceding claim, wheein a handle or handle sections are applied to the handle portion.

8. A method of manufacturing a bolstered hand tool substantially as any of the embodiments hereinbefore described with reference to Figures 2 to 10 of the accompanying drawings.

9. A hand tool produced according to the method of any of the preceding claims.