SAW TEETH CONFIGURATION AND ITS GRINDING METHOD

Abstract: The invention relates to hacksaw blades formed from unitary strip material or from bimetallic strip with each tooth formed wholly from the hard metal part of the strip. With conventional blades produced by conventional machining techniques such as milling, chip removal during sawing is not effected efficiently, consequent on the relatively rough nature of the e.g. milled faces of the teeth. The object of the invention is to improve hacksaw blades and is achieved by a method comprising forming along one edge of appropriate strip material, teeth at an appropriate pitch and depth, and where each tooth has first, or primary (3), and secondary (4) flank faces rearwardly a tooth tip (2) and a rake face (5) extending from the tip at a required rake angle, each tooth being formed by grinding at least the length of the first, or primary flank face (3), and to a commensurate length over the rake face extending from the tip. Preferably, the full tooth including the root between adjacent teeth is formed by grinding.

Description: SAW TEETH CONFIGURATION AND ITS GRINDING METHOD This invention relates to hacksaw blades. Traditionally, hacksaw blades have been formed by forming a tooth profile along one edge of strip material, with a flank rearwardly of a cutting tip of a tooth extending to a root or gullet between two teeth and a rake face forwardly of the tip at a required rake angle, also extending to the root or gullet between the teeth. Considerable attention has been given over many years to rake angle and to the angle of the flank, and to other parameters such as tooth pitch, and required angles at which the teeth are to be set, all largely dictated by the function that is required of the hacksaw blade. Other areas to which considerable attention has been given are, such as, the material and composition of strip material from which a hacksaw blade is to be formed with the strip material either of unitary or bimetallic form. Saw blades, are known where the tooth profile is formed by a milling technique, with the tooth formed wholly from the unitary material of the blade, or by milling a tooth in a bimetallic strip to provide a triangular tooth tip of a first hard material with the remainder of the tooth formed from a tough second material. Such a construction in the form of a band saw blade, is disclosed in British Patent No. 2044171. Milling of a tooth profile whilst effective from a production viewpoint with either a strip of unitary metal or a bimetallic strip, leaves a machined surface to the tooth profile that is relatively rough and not conducive to efficient removal of chips removed from a metallic body during the use of the saw blade. The objects of the present invention are to provide a hacksaw blade and a method of production of a hacksaw blade whereby considerably enhanced cutting characteristics are provided. According to a first aspect of the present invention, a hacksaw blade comprises saw teeth formed along one edge of appropriate strip material, each tooth having rearwardly of its tip, ". a first, or primary, flank face at a first acute angle to the horizontal plane in which the tip of the tooth lies, said first, or primary, flank face extending to a secondary flank face at a greater acute angle to that of the first, or primary, flank face, and there being a rake face to each tooth extending from the tip at a required rake angle, each of said secondary flank face and rake face extending to a root to opposite sides of a respective tooth and each tooth being formed by grinding the first, or primary, flank face, the secondary flank face and the rake face of each tooth. Each tooth may also be formed with a cutting edge by the provision of an angled face extending across the thickness of the blade strip at least over the length of the first, or primary, flank face, and a commensurate length of the rake face extending from the tip. Preferably, the angled face across the thickness of the strip extends along at least a part of the length of the secondary flank face and over a then-commensurate length of the rake face of the tip. Still further preferably, the first, or primary, flank face is at an angle of 16° to 37°, the secondary flank face is at an angle of 40° to 50°, and the flank face to the tip at a positive rake angle of 1° to 10°. The radius of the root between adjacent teeth is not of itself particularly critical and would be determined as a function of the rake angle of the rake face, the angle of the secondary flank face, the tooth pitch, and the tooth depth, of a particular hacksaw blade. According to a second aspect of the present invention, a method of producing a hacksaw blade comprises forming along one edge- of appropriate strip material teeth at an appropriate pitch and depth, where each tooth has first, or primary, and secondary flank face to one (rear) side of a tip and a rake face to the tip at a required rake angle, each tooth being formed by grinding at least the length of the first, or primary flank face, and to a commensurate length over the rake face extending from the tip. Each tooth may also be ground to provide an angled surface across the thickness of the strip material and to provide a cutting edge to each tooth at least over the tip portion thereof. Each tooth may, however, be formed by grinding over at least a part of the length of the secondary flank face and over a then-commensurate length of the rake face. Still further preferable is the formation of the full tooth by grinding including the root between adjacent teeth. Equally possible is the employment of appropriate form grinding whereby to create simultaneously teeth of the required peripheral profile and the angled surface to form the cutting edge. The grinding of the faces to create the tooth profile and its cutting edge has a significant effect on the cutting characteristics of blades in accordance with the invention in comparison with those conventional blades of the prior art. This stems from the forming of the teeth by grinding, the ground faces of the teeth being substantially smoother than with conventional forms of tooth production, and as a result of which chips and swarf removed from a body of metal * being cut by a saw blade of the invention are removed from the vicinity of the bottom of the slot being cut with considerably greater efficiency, and as a direct consequence, the cutting action of a saw blade of the invention is enhanced noticeably over conventional blades. One embodiment of the invention will now be described with reference to the accompanying drawings, in which:- Figure 1 shows part of a hacksaw blade with a tooth profile in accordance with the invention; Figure 2 corresponds to Figure 1 but shows a part of a hacksaw blade with a tooth profile of conventional structure; and Figure 3 is a graphical representation of test results comparing the cutting performance of the hacksaw blades of Figures 1 and 2. In Figure 1, a hacksaw blade 1 has a tooth profile where each tooth has, rearward of its tip 2, a first or primary, flank face 3 at an acute angle to the horizontal plane in which the tips of the teeth lie, said angle lying between 16° and 37°, leading to a secondary flank face 4 at an acute angle of between 40° and 50°. Forwardly of the tip 2 is a rake face 5, at a positive rake angle of between 1° and 10°. The secondary flank face 4 of one tooth and the rake face 5 of the adjacent tooth both extending to a root 6 between the adjacent teeth. Each tooth, at least over the length of the first, or primary flank face 3 and over a commensurate length of the rake face 5, are ground across the thickness of the blade to provide surfaces considerably more smooth than is the case with conventional production e.g. milling. Each tooth may be ground at an angle across the thickness of the blade and may also be appropriately set in accordance with conventional practice. The blade, across its width from the back edge to the tip, may be of unitary material, but equally the blade could be bi-metallic with a body of a first material with a strip of a second material along one edge and in which the teeth are wholly formed. Blades in accordance with the invention where first, or primary, flank faces, secondary flank faces and rake surfaces at a positive rake angle were all formed by grinding, were subjected to test in direct accordance with the requirements of BS 1919:1983, as were comparable blades of conventional construction with milled edges and as are illustrated in Figure 2. The comparable test results were as follows. The tests comprise the banding together of ten strips of nominally identical stainless steel all of the nominal cross-section 25 x 2.5 mm, employment of ten strips being to ensure heterogeniety of the sample. Ten such banded sets of strips were each then completely severed by a number of conventional blades and blades in accordance with the invention. The number of strokes needed by each blade to completely sever 10 strips were recorded and are: Strokes for Cut Indicated 1st 2nd 3rd 4th 5th 6th 7th 8th 9th 10th 1. 511 545 557 576 609 632 628 639 656 657 2. 520 561 574 581 565 578 582 595 598 602 3. 479 542 565 573 556 559 604 589 598 597 .4. 484 513 549 558 559 562 .575 582 590 590 5. 421 460 476 476 477 48-3 482 498 508 508 6. 405 449 471 493 486 488 485 488 491 500 7. 410 426 432 444 445 462 462 477 473 472 8. 407 435 471 463 468 462 476 467 500 509 In the above results, blades numbers 1 to 4 were of conventional construction and blades numbers 5 to 8 were in accordance with the invention. Figure 3 is a graphical representation of the average of the results as detailed above, from which it is immediately apparent that blades in accordance with the invention have considerably enhanced cutting characteristics in comparison with blades of conventional construction.

Claims: CLAIMS 1. A hacksaw blade comprising saw teeth formed along one edge of appropriate strip material, each tooth having rearwardly of its tip, a first, or primary, flank face at a first acute angle to the horizontal plane in which the tip of the tooth lies, said first, or primary, flank face extending to a secondary flank face at a greater acute angle to that of the first, or primary, flank face, and there being a rake face to each tooth extending from the tip at a required rake angle, each of said secondary flank faces and rake faces extending to a root to opposite sides of a respective tooth and each tooth being formed by grinding the first, or primary, flank face, the secondary flank f ce- and the rake face of each tooth. 2. A hacksaw blade as in Claim 1, wherein each tooth is formed with a cutting edge by the provision of an angled face extending across the thickness of the blade strip at least over the length of first, or primary, flank face, and a commensurate length of the rake face extending from the tip. 3. A hacksaw blade as in Claim 1 or Claim 2, wherein the first, or primary, flank face is at an angle of 16° to 37°. 4. A hacksaw blade as in any of Claims 1 to 3, wherein the secondary flank face is at an angle of 40° to 50°. 5. A hacksaw blade as in any of Claims 1 to 4, wherein the rake face to the tip is at a positive rake angle of 1° to 10 ° . 6. A method of producing a hacksaw blade comprising forming along one edge of appropriate strip material, teeth at an appropriate pitch and depth, where each tooth has first, or primary, and secondary flank faces rearwardly of a tooth tip and a rake face extending from the tip at a required rake angle, each tooth being formed by grinding at least the length of the first, or primary flank face, and to a commensurate length over the rake face extending from the tip. 7. A method as in Claim 6, wherein each tooth is also ground to provide an angled surface across the thickness of the strip material and to provide a cutting edge to each tooth at least over the tip portion thereof. 8. A method as in Claim 6, wherein each tooth is formed by grinding over at least a part of the length of the secondary flank face and over.a then-commensurate length of the rake face. 9. A method as in Claim 6, wherein full teeth are formed by grinding. 10. A method as in any of Claims 6 to 8, wherein each tooth is produced by form grinding whereby to create simultaneously, teeth of the required profile and an angled surface across the strip thickness.

Inventors: COX NORMAN, COX, NORMAN
Applicants: COX NORMAN, NEIL HOLDINGS LTD JAMES, COX, NORMAN, JAMES NEILL HOLDINGS LIMITED
Application year: 1995
Main classification: B23D61
IPC codes: B23D61, B23D65