The present invention relates to blades, for example for use as bandsaw blades, jigsaw blades, hacksaw blades or handsaw blades.
An aspect of the invention provides a blade comprising a strip having a main body portion and an edge portion, and
cutting medium secured to the strip along the edge portion,
wherein the cutting medium is a grit secured to the strip by brazing.
The edge portion may be thinner than the main body portion.
The edge portion may meet the main body portion at a step on at least one face of the strip. The edge portion may meet the main body portion at a step on both faces of the strip.
The cutting medium may be secured to the strip only on surfaces of the edge portion.
The edge portion may have a surface which meets the main body portion at two locations forming a neck between the edge portion and the main body portion, the edge portion having a convex surface between the locations. The convex surface may be a substantially continuous curved surface. The cutting medium may comprise particles of a size which is less than the radius of curvature of the convex surface.
The edge portion may have an edge face and side flanks extending from the edge face to the main body portion, the face and flanks meeting at edges extending along the strip and spaced from the main body portion. The edge face may be concave. At least one of the flanks may be concave. Both flanks may be concave. The edge face and/or at least one of the flanks may have the form of irregular concavities. The, or at least one of the concavities, may provide a channel receiving braze material. The cutting medium may comprise particles which are sufficiently large to be received within the or a channel and to project out beyond the channel.
The main body may have at least one through aperture formed therein. There may be a plurality of through apertures spaced along the strip. At least part of the circumference of the or an aperture may be tapered in thickness to deflect cut material from the aperture.
The cutting medium may be diamond, tungsten carbide, cubic boron nitride, a ceramic or a ceramic-base material or a cermet.
The blade may be a reciprocating blade. The blade may be a linear edge blade. The blade may be for a bandsaw, jigsaw, hacksaw, handsaw reciprocating saw or holesaw.
In another aspect, the invention provides a method of making a blade, comprising:
providing a strip having a main body portion and an edge portion;
providing a cutting medium in the form of a grit;
brazing the cutting medium to the strip along the edge portion.
The edge portion may be thinner than the main body portion.
Braze material may be applied to the edge portion before the cutting medium is introduced.
The braze material may include adhesive material for holding the braze material to the edge portion, and to hold the cutting medium prior to brazing. The strip carrying the braze material and the cutting medium may be heated to braze the cutting medium to the strip.
The strip may be formed to provide a step on at least one face of the strip, at which the edge portion meets the main body portion. A step may be formed on both faces of the strip.
The cutting medium may be secured to the strip only on surfaces of the edge portion.
The edge portion may be formed to have a surface which meets the main body portion at two locations forming a neck between the edge portion and the main body portion, and to have a convex surface between the locations. The convex surface may be a substantially continuous curved surface. The cutting medium may be provided as particles of a size which is less than the radius of curvature of the convex surface.
The edge portion may be formed to have an edge face and side flanks extending from the edge face to the main body portion, the face and flanks meeting at edges extending along the strip and spaced from the main body portion. The edge face may be formed to be concave. At least one of the flanks may be formed to be concave. Both flanks may be formed to be concave. The edge face and/or at least one of the flanks may have the form of irregular concavities. Braze material may be provided within a channel provided by at least one of the concavities. The cutting medium may be provided as particles which are sufficiently large to be received within the or a channel and to project out beyond the or a channel.
At least one through aperture may be formed in the main body. A plurality of through apertures, spaced along the strip, may be formed in the main body. At least part of the circumference of the or an aperture is formed with a thickness taper to deflect cut material from the aperture. The cutting medium may be diamond, tungsten carbide, cubic boron nitride, a ceramic or a ceramic-base material or a cermet.
The blade may be formed as a reciprocating blade. The blade may be a linear edge blade. The blade may be formed for a bandsaw, jigsaw, hacksaw, handsaw, reciprocating saw or holesaw.
Examples of the present invention will now be described in more detail, by way of example only, and with reference to the accompanying drawings, in which:
a to 8d illustrate steps in the manufacture of a blade.
The diamond is preferably a grit of industrial diamond. Diamond grit is commonly measured by reference to mesh sizes, i.e. the smallest mesh through which the grit particles will pass. Example mesh sizes envisaged for making the blade being described, are in the range 0.1 mm to 1.5 mm mesh size.
The strip 2 may be spring steel.
The braze and brazing process will be described below, in more detail, with reference to
In this example, the strip 12 has three principal dimensions illustrated at 20, namely a length 20a, a width 20b and a thickness 20c. The length 20a is much greater than the width 20b. The width 20b is greater than the thickness 20c. In this example, the thickness 20c in the main body 14 is greater than the thickness 20c in the edge portion 16, as noted above. The thickness of a blade is often called its “kerf”. Accordingly, the edge portion of this example has reduced kerf, relative to the main body portion 14.
The change in thickness of the strip 12 occurs at steps 22 on the faces of the strip 12. In this example, there is a step 22 on both faces of the strip. In other examples, a step may be formed on only one face, the other face of the strip being continuous. The grit 18 is secured to the strip 12 only on surfaces of the edge portion 16.
At one or both ends of the strip 12, mountings 24, illustrated schematically in
Various profiles are envisaged for the main body 14 and edge portion 16, in which the edge portion is thinner than the main body portion. Examples are illustrated in
In the example of
In more geometrical terms, substantially any position on the convex surface 26 has a centre of curvature 32 which is on the same side of the surface as the material of the edge portion 16, and a radius of curvature R. The location of the centre of curvature 32, and the size of the radius of curvature R may change from position to position, around the edge portion 16, but change smoothly and continuously, without step changes.
In this example, the grit 18 coating the surface 26 is in the form of a fine powder of particles 34 suspended in braze material 36. The particle size (such as the average diameter) is less than the radius of curvature of the surface 26. In the illustrated example, the size of the particles 34 is much less than the radius of curvature at any position on the surface 26. The convex form of the surface 26 allows relatively fine particles to be used in this manner, without edges, corners or other discontinuities on the surface 26 being exposed between particles 34. This is expected to allow the blade 10 to be used in applications which require a workpiece to be cut with curves or corners in the line of cut. The locations 28 provide channels along which swarf, cuttings or other debris can move away from the cutting face.
In the examples of
In the example of
In the example of
When the blade 10 is in use, making a cut, the edge portion 16 penetrates the workpiece 52 (illustrated in
However, profiles such as those illustrated in
The remaining drawings illustrate in simple fashion a possible manufacturing process for providing blades of the types described above.
In
Braze material 36 is then applied to the edge portion 16, prior to the introduction of grit 18. The braze material 36 is in the form of a paste, containing a braze medium in particle form, suspended in an adhesive component which allows the braze medium to be retained temporarily in place on the edge portion 16. The braze material 36 may be a nickel-based alloy. Commercial examples include the Nicrobraze LM product of Wall Colmonoy Corp.
The adhesive material may be a starch-based paste, for example.
The adhesive material also allows grit 18 of cutting medium to be cascaded onto the edge portion 16, sticking to the adhesive material upon contact. The result is a temporary coating of the edge portion 16, by means of the adhesive, by particles of braze medium and cutting medium grit. This coating is illustrated in
The coated strip 12 is then exposed to heat 66, causing the brazing process to take effect, thereby permanently securing the grit 18 to the edge portion 16. The brazing process may, for example, require the materials to be brought to a temperature in the region of about 800° C. to 1100° C. for a few seconds. This may be achieved as a continuous process, passing the strip lengthwise through an oven. The oven may contain an inert gas, such as nitrogen or argon.
In the examples described above, the cutting medium has been described as diamond grit. Other materials can be used. Examples include tungsten carbide and cubic boron nitride. Ceramic or ceramic-based materials may be used. A cermet material may be used. A cermet material is a composite material of ceramic and metal materials. Cermet materials can provide worthwhile combinations of high temperature resistance and hardness properties of a ceramic material, with mechanical properties of a metal.
In all of the examples, blades can be formed for use as bandsaw blades, jigsaw blades, hacksaw blades, handsaw blades. These are all examples of linear edge blades. Linear edge blades, in the form of strip of the type described, can be formed into holesaws. Strip of the type described can be used for reciprocating saws.
Many variations and modifications can be made to the apparatus and methods described above, without departing from the scope of the invention.
Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.
Number | Date | Country | Kind |
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0621150.2 | Oct 2006 | GB | national |
This application is a continuation-in-part (CIP) of PCT International Patent Application No. PCT/GB2007/003911, filed Oct. 12, 2007, pending, which claims the benefit of Great Britain Patent Application No. 0621150.2, filed Oct. 24, 2006, the entire contents of each of which are hereby incorporated by reference in this application.
Number | Date | Country | |
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Parent | PCT/GB2007/003911 | Oct 2007 | US |
Child | 12211381 | US |