Annular cutter

Abstract

An annular cutter having a cylindrical side wall provided with cutting teeth spaced circumferentially around its lower end, the inner periphery of .[.each tooth.]. .Iadd.a plurality of teeth .Iaddend.being radially relieved to provide a narrow margin at the inner side of .[.each tooth.]. .Iadd.the plurality of teeth .Iaddend.directly behind the cutting edge thereof and simultaneously provide a large escape path for chips and an enlarged coolant passageway directly adjacent the cutting teeth.

I claim: 
     
       1. An annular cutter having a body provided with a generally cylindrical side wall, said side wall having a plurality of circumferentially spaced teeth around its lower end and a plurality of spiral flutes around its outer periphery extending upwardly from between the successive teeth, each tooth having at least one radially extending cutting edge, there being gullets extending radially outwardly from the inner periphery of the side wall to said flutes between successive teeth to facilitate the discharge of chips cut by said cutting edges radially outwardly and upwardly into said flutes, each gullet having a radially extending trailing face extending upwardly from the radially inner portion of each cutting edge, each tooth having a radially inner back off face inclining downwardly and radially outwardly and an outer back off face inclining downwardly and radially inwardly, said back off faces intersection in a sharp crest defined by a line which extends circumferentially rearwardly from the front face of each tooth, said crest, when the cutter is rotated and advanced into the surface of a workpiece, initiates the cutting action by forming a V-shaped groove in said surface, the inner periphery of .[.each tooth.].ep  .Iadd.a plurality of said teeth .Iaddend.being relieved in a radially outward direction to provide a circumferentially extending radial clearance space between the inner periphery of .[.the tooth.]. .Iadd.each of said plurality of teeth .Iaddend.and the central slug formed in the workpiece by the cutter, said clearance space extending rearwardly from a generally vertically extending line spaced rearwardly from the line of intersection of said inner periphery and the trailing face of .[.each.]. .Iadd.the .Iaddend.gullet .Iadd.of each of said plurality of teeth .Iaddend., the inner peripheral surface of each .[.tooth.]. .Iadd.of said plurality of teeth .Iaddend.between said vertically extending line and said line of intersection forming a margin therebetween having a circumferential width .[.of between 0.002" to 0.040".]., said margins forming .[.a.]. segments of a cylindrical surface concentric with the central axis of the cutter, the inner periphery of each .[.tooth.]. .Iadd.of said plurality of teeth .Iaddend.being relieved such that said clearance space is progressively wider radially in a circumferentially rearward direction and extends rearwardly on each .[.tooth.]. .Iadd.of said plurality of teeth .Iaddend.to the next successive rearward gullet. 
     
     
       2. A cutter as called for in claim 1 wherein said clearance space is defined by a generally vertical surface which inclines radially outwardly from said vertically extending line at an angle of at least between about 3° to 7° to the tangent of said inner periphery of said line. 
     
     
       3. A cutter as called for in claim 2 wherein .[.at at least most of said teeth.]. said vertically extending line is spaced rearwardly from said line of intersection to form a margin having a circumferential width of between about 0.002 to .[.0.015".]. .Iadd.0.040".Iaddend.. 
     
     
       4. A cutter as called for in claim 2 wherein said vertically extending line is inclined slightly rearwardly relative to said line of intersection such that said margin is wider at its upper end than its lower end. 
     
     
       5. A cutter as called for in claim 2 wherein said margin is at least coextensive in height with said line of intersection. 
     
     
       6. A cutter as called for in claim 2 wherein .[.each tooth is.]. .Iadd.a plurality of said teeth are .Iaddend.provided with a plurality of circumferentially staggered cutting edges, the radially innermost cutting edge being disposed forward in the direction of rotation of the cutter from the next radially adjacent cutting edge. 
     
     
       7. A cutter as called for in claim 6 wherein said vertical surface is flat and inclines radially outwardly at an angle of about 12° to said tangent. 
     
     
       8. A cutter as called for in claim 2 wherein said body has an axially extending coolant passageway therethrough. 
     
     
       9. A cutter as called in for claim 6 wherein said crest extends circumferentially rearwardly from the radially outermost cutting edge. .Iadd. 
     
     
       10.  An annular cutter having a body provided with a generally cylindrical side wall, said side wall having a plurality of circumferentially spaced teeth around its lower end and a plurality of flutes around its outer periphery extending upwardly from between the successive teeth, each tooth having at least one radially extending cutting edge, and gullets extending radially outwardly from the inner periphery of the side wall communicating with said flutes between successive teeth to facilitate the discharge of chips cut by said cutting edges radially outwardly and upwardly into said flutes, each gullet having a radially extending trailing face extending upwardly from the radially inner portion of each cutting edge, the inner periphery of at least some of said teeth being relieved in a radially outward direction to provide a circumferentially extending radial clearance space between the inner periphery of each of said plurality of teeth and the central slug formed in the workpiece by the cutter, said clearance space extending rearwardly from a generally vertically extending line spaced rearwardly from the line of intersection of said inner periphery and the tailing face of the gullet of each of said plurality of teeth, said clearance space being defined by a generally vertical surface which inclines radially outwardly from said vertically extending line, the inner peripheral surface of each of said plurality of teeth between said vertically extending line and said line of intersection forming a margin therebetween having a circumferential width, said margins forming segments of a cylindrical surface concentric with the central axis of the cutter, said inner periphery of each of said some of said teeth being relieved such that said clearance space extends rearwardly on each of said teeth to the next successive rearward gullet. .Iaddend. .Iadd.11. A cutter as called for in claim 10, wherein said clearance space has a progressively increasing width in a rearward direction. .Iaddend. .Iadd.12. A cutter as called for in claim 10 wherein said vertically extending line is spaced rearwardly from said line of intersection to form a margin having a circumferential width of between about 0.002 to 0.040". .Iaddend. .Iadd.13. A cutter as called for in claim 10 wherein said vertically extending line is inclined slightly rearwardly relative to said line of intersection such that said margin is wider at its upper end than its lower end. .Iaddend. .Iadd.14. A cutter as called for in claim 10 wherein a plurality of said teeth are provided with a plurality of circumferentially staggered cutting edges, a radially innermost cutting edge being disposed forward in the direction of rotation of the cutter 
     
     
        from the next radially adjacent cutting edge. .Iaddend. .Iadd.15.  A cutter as called for in claim 10 wherein said body has an axially extending coolant passageway therethrough. .Iaddend. .Iadd.16. An annular cutter having a body provided with a generally cylindrical side wall, said side wall having a number of circumferentially spaced teeth around its lower end with chip passages extending upwardly from between the successive teeth, each tooth having at least one radially extending cutting edge, the inner periphery of a plurality of said teeth being relieved in a radially outward direction to provide a circumferentially extending radial clearance space between the inner periphery of said plurality of teeth and a central slug formed in the workpiece by the cutter, said clearance space being defined by a generally vertical surface which inclines radially outwardly from said generally vertical line, said clearance space extending rearwardly from a generally vertical line spaced rearwardly from the radially innermost portion of said respective cutting edge forming a margin therebetween having a circumferential width, said margin forming a segment of a cylindrical surface concentric with the central axis of the cutter. .Iaddend. .Iadd.17. A cutter as called for in claim 16, wherein said clearance space has a progressively increasing width in a rearward direction. .Iaddend. .Iadd.18. A cutter as called for in claim 16, wherein said margin has a circumferential width of between about 0.002 to 0.040". .Iaddend. .Iadd.19. A cutter as called for in claim 16, wherein said body has an axially extending coolant passage therethrough. .Iaddend. .Iadd.20. A cutter as called for in claim 16, wherein the inner periphery of each of said plurality of teeth is relieved such that said clearance space extends rearwardly on each of said plurality of teeth to the next successive rearward chip passage. .Iaddend. 
     
     
        .Iadd.21.  An annular cutter having a body provided with a generally cylindrical side wall, said side wall having a plurality of circumferentially spaced teeth around it lower end, each tooth having at least one radially extending cutting edge, gullets extending radially outwardly from the inner periphery of said side wall between successive teeth to facilitate the discharge of chips cut by said cutting edges outwardly and upwardly, said gullets having a generally radially extending trailing face extending outwardly from the radially inner portion of said cutting edge, the inner periphery of at least some of said teeth being relieved in a radially outward direction to provide a circumferentially extending radial clearance space between the inner periphery of the tooth and a central slug formed in a workpiece by said annular cutter, said clearance space extending rearwardly from a line spaced rearwardly and generally parallel to a line of intersection of said inner periphery and said trailing face of said gullet, said inner peripheral surface between the line of intersection and said parallel line forming a margin therebetween, said margins forming segments of a cylindrical surface concentric with the inner periphery of said cutter, said inner periphery adjacent each margin being relieved such that said clearance space is progressively wider radially in a circumferentially rearward direction. .Iaddend. .Iadd.22. A cutter as called for in claim 10, wherein said generally vertical surface is defined by a segment of a circumferential arc. .Iaddend. .Iadd.23. A cutter as called for in claim 21 wherein said clearance extends rearwardly into the next successive rearward gullet. .Iaddend. .Iadd.24. A cutter as called for in claim 21 wherein said body has a generally axially extending coolant passage therethrough. .Iaddend. .Iadd.25. A cutter as called for in claim 21 wherein said margins have a circumferential width of about 0.002" to about 0.040". .Iaddend. 
     
     
        .Iadd.     A cutter as called for in claim 16, wherein said generally vertical surface is defined by a segment of a circumferential arc. .Iaddend. .Iadd.27. A cutter as called for in claim 16, wherein said clearance space is defined by a generally vertical surface. .Iaddend.