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Title: Boring tool for working bores of small diameter
Claims: We claim: 1. A boring tool for working a bore of small diameter in a workpiece comprising: a shaft of circular cross-section having a clamping part for supporting the tool and a neck part extending from the clamping part and terminating in a foward end; a cutting plate having cutting points, said cutting plate being completely within the cross-section of said neck part except for minimal projection of a single said cutting point sideways beyond the periphery of said neck part, and means eccentrically locating and removably affixing said cutting plate in snugly recessed relation in said forward end of said neck part for interchanging of cutting plates and replacing of a used cutting point with another cutting point by reorientation of said cutting plate; a semicircular cross-section cuttings channel in the peripheral surface of said neck part, said cuttings channel opening forwardly of the neck part at and in communication with said cutting plate, said cuttings channel extending rearwardly toward said clamping part and being spiralled in the direction of rotation and feed of the workpiece with respect to the boring tool, the spiralling of said cuttings channel approaching, at maximum, one-third of a pitch, the surface of the cuttings channel being smoothly ground, the angle of pitch (.alpha.) of said cuttings channel being about 70.degree. to 80.degree., the boring tool having only a single cutting plate, the only structure protecting laterally from said neck part to contact the wall of the bore being said single cutting point of said cutting plate, said neck part having only a single said cuttings channel and having, intermediate the ends of said cuttings channel, a cross-section generally of half-moon shape. 2. The boring tool of claim 1, in which the laterally central portion of the semicircular section, spiralled cuttings channel lies adjacent the central axis of said neck part, in the longitudinally central portion of such channel. 3. The boring tool of claim 2, wherein the longitudinal extent of said spiralled cuttings channel somewhat exceeds the depth of a workpiece bore to be worked by the tool, the cutting plate being arranged substantially horizontally on said neck part with the adjacent part of said cuttings channel opening upwardly and sidewardly toward said cutting point, the upper face of said cutting plate being exposed, the cuttings channel spiraling rearwardly and downwardly along the side of said neck part from which said cutting point extends, and facing substantially downwardly at its rearward end, so as to rearwardly channel cuttings from the cutting plate with the assistance of gravity and drop same downwardly from said neck portion at the outer end of the workpiece and immediately adjacent the rear end of the cuttings channel when the finished depth of bore has been attained. 4. The boring tool of claim 3, in which the cuttings channel becomes shallow and terminates at the rear end thereof adjacent said clamping part. 5. The boring tool of claim 2, in which the cutting point projects no more than about 1/2 mm. beyond the circular cross-section of said neck part, said boring tool being arranged for producing relatively small diameter bores in the range of about 8 to 20 mm. 6. The boring tool of claim 5, in which said gradient angle (.alpha.) is 75.degree.. 7. The boring tool of claim 2, in which, as seen from the forward end of said boring tool, the top surface of said cutting plate lies in horizontal diametral plane of said neck part and extends from said cutting point horizontally into the center portion of said neck part, the front end of said semicircular cross-section spiral cuttings channel having one side extending upwardly substantially from said horizontal diametral plane and its other side cut away to provide a planar, decklike surface lying in said horizontal diametral plane of said neck part, said deck surface extending radially inward of said neck part beyong said cutting plate and extending rearward along said neck beyond said cutting plate, the face of said semicircular cross-section cuttings channel angling downwardly from the rear edge of said deck surface as it spirals rearwardly therefrom, the forward portion of said deck surface having a recess opening forwardly through the front end of said neck and shaped to snugly receive said cutting plate with a minor front edge portion of said cutting plate overhanging forwardly beyond said recess, said cutting point being the radially outer tip of said cutting plate front edge portion, the top of said cutting plate being flush with the top of said deck surface such that chips from said cutting point pass rearwardly along the top of said cutting plate and deck surface to reach the semicircular cross-section portion of said spiral cuttings channel. 8. The boring tool of claim 7, in which said cutting plate is triangular in plan, with the innermost side thereof parallel to the axis of said neck part and located near the edge of said deck surface, the remaining two sides of said cutting plate converging laterally outward to said cutting point such that the latter slightly overhangs the peripheral surface of said neck part. 9. The boring tool of claim 7, in which said cutting plate is triangular in plan and has one side approximately parallel to the adjacent edge of said spiral channel and extending slightly thereinto, the front side of said triangular cutting plate paralleling a diametral plane of said neck part and extending from the front end of said one side of said cutting plate to said cutting point, the remaining side of said triangular cutting plate extending transverse to the spiral axis of said channel. 10. The boring tool of claim 2, in which the periphery of said neck part, outside said semicircular channel and for the length of said channel and circumferentially from one channel edge to the other, is smoothly circular and without raised ridges, only said single cutting point extending radially beyond the smooth cylindrical periphery of said neck part. 11. A boring tool for working a workpiece bore of small diameter, comprising: a shaft of circular cross-section comprising a clamping part for supporting said boring tool and a neck part extending forwardly from said clamping part and having a free forward end for penetrating the workpiece bore; a cutting plate mounted on said forward free end of said neck part and having a cutting point which projects sidewardly beyond said neck part, said cutting plate being completely within the circular cross-section of said neck part except for said projecting cutting point, said neck part having a channel for cuttings extending rearwardly from said cutting plate, said channel being spiralled in the direction of rotation and feed of the workpiece with respect to said boring tool, said cuttings channel having a semicircular cross-section; a cuttings breaker mounted on the upper side of said cutting plate and extending laterally to a location close above said cutting point, said cuttings breaker having a longitudinal side adjacent said cutting point and extending axially with respect to said neck part and having a cuttings breaking channel running parallel to the axis of said neck part at said longitudinal side and opening toward said cutting plate and said cutting point. 12. The boring tool of claim 11, in which the cross-section of said cuttings breaking channel widens axially from its forward end to its rear end, with the widened rear end of such cuttings breaking channel opening into said spiral cuttings channel. 13. The boring tool of claim 12, in which said cuttings breaking channel is of approximately semicircular cross-section. 14. The boring tool of claim 12, in which the cuttings breaker channel opens laterally through a slit which extends the entire length of said cuttings breaker, said longitudinal side of said cuttings breaker and said cutting plate being opposed across said slit. 15. The boring tool of claim 11, in which the external contour of the cuttings breaker is substantially semicylindrical with the radius corresponding to the radius of said neck part, said cuttings breaker substantially filling the forward portion of said cuttings channel and substantially completing the circular cross-section of said neck part adjacent the front end of the latter. Other info: Inventors: Eckle, Otto (Lochgau, DT) Grzegorz, Hans (Besigheim, DT) Application Number: 515670 Filing Date: 1974-10-17 Publication_date: 1976-06-15 Assignee: KOMET Stahlhalter-und Werkzeugfabrik, Robert Breuning GmbH (Besigheim, DT) Primary Class(es): 408/199 408/713 Other Classes: US Patent Ref:
Other Refs:
Primary Examiner: Simpson, Othell M. Assistant Examiner: Briggs, William R. Attorney: Woodhams, Blanchard and Flynn |
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