Button bit

Abstract

A button bit is disclosed of the type that is rotatable in a predetermined direction of rotation (R) around a centre axis (C) and includes a number of spaced-apart peripheral buttons, which protrude forward from a front end surface to which an envelope surface connects having a rotationally symmetrical shape, the individual peripheral button being tilted partly in relation to the centre axis (C) of the drill bit, partly in the forward direction of rotation (R) in relation to the surface from which the button protrudes. The hole for the individual peripheral button mouths in a countersunk entering surface which is planar, ring-shaped and extends perpendicularly to the centre axis (C 1 ) of the hole. By tipping the button in the forward direction of rotation, the same will operate aggressively and efficiently. Also, the peripheral button may be mounted in accurate drilled apertures which are simple to provide, despite the complex space geometry predicament.

1 . A button bit of the type that is rotatable in a predetermined direction of rotation around a centre axis, the button bit comprising:
 a body; and   a number of spaced-apart peripheral buttons each positioned in a hole,   wherein the buttons protrude forward from a front end surface to which an envelope surface connects,   wherein the body has a rotationally symmetrical shape,   wherein at least one individual peripheral button is tilted partly in relation to a centre axis of the bit, and partly in a forward direction of rotation in relation to a surface from which the button protrudes,   wherein a mouth of the hole for the individual peripheral button includes a countersunk entering surface which is planar and ring-shaped, and   wherein the countersunk entering surface extends perpendicularly to a centre axis of the hole.   
   
   
       2 . The button bit according to  claim 1 , wherein the individual peripheral button has a centre axis tilted at an acute angle in relation to the centre axis of the bit and in that the countersunk entering surface is delimited by a cylinder surface, the depth of which decreases in a direction from a rotationally leading end toward a trailing end. 
   
   
       3 . The button bit according to  claim 2 , wherein the individual peripheral button, in addition to a tapering tip, comprises a cylindrical base part that is fixed in a cylindrical hole, which mouths in a surface via a mouth opening having an oval shape. 
   
   
       4 . The button bit according to  claim 1 , wherein the centre axis of the individual peripheral button is tilted not only at a primary tip angle (α) in relation to the centre axis of the bit, but also at a secondary tip angle (ε) in relation to a centre plane (MP), wherein the centre plane (MP) is oriented perpendicular to the surface from which the button protrudes and intersects the mouth of the hole halfway between the rotationally leading and trailing end points along a borderline of the hole. 
   
   
       5 . The button bit according to  claim 4 , wherein the secondary tip angle (ε) is at least 5°. 
   
   
       6 . The button bit according to  claim 5 , wherein the secondary tip angle (ε) is at most 20°. 
   
   
       7 . The button bit according to  claim 4 , wherein all peripheral buttons are tilted at said primary tip angle (α) as well as at said secondary tip angle (ε). 
   
   
       8 . The button bit according to  claim 7 , wherein the secondary tip angle (ε) is at least 5°. 
   
   
       9 . The button bit according to  claim 8 , wherein the secondary tip angle (ε) is at most 20°. 
   
   
       10 . The button bit according to  claim 7 , wherein the peripheral buttons are arranged along a ring-shaped, peripheral cone surface, the cone angle (β) of which is obtuse, and which is located between the envelope surface and a central front surface from which a number of centre buttons protrude forward, a part of the individual peripheral button protruding peripherally in relation to the envelope surface. 
   
   
       11 . The button bit according to  claim 10 , wherein the individual peripheral button, in addition to a tapering tip, comprises a cylindrical base part that is fixed in a cylindrical hole, which mouths in a surface via a mouth opening having an oval shape. 
   
   
       12 . The button bit according to  claim 11 , wherein the oval shape has a major axis extending tangentially along the cone surface and a minor axis extending radially along the cone surface. 
   
   
       13 . The button bit according to  claim 4 , wherein the peripheral buttons are arranged along a ring-shaped, peripheral cone surface, the cone angle (β) of which is obtuse, and which is located between the envelope surface and a central front surface from which a number of centre buttons protrude forward, a part of the individual peripheral button protruding peripherally in relation to the envelope surface. 
   
   
       14 . The button bit according to  claim 13 , wherein the individual peripheral button, in addition to a tapering tip, comprises a cylindrical base part that is fixed in a cylindrical hole, which mouths in a surface via a mouth opening having an oval shape. 
   
   
       15 . The button bit according to  claim 14 , wherein the oval shape has a major axis extending tangentially along the cone surface and a minor axis extending radially along the cone surface. 
   
   
       16 . The button bit according to  claim 3 , wherein the individual peripheral button, in addition to a tapering tip, comprises a cylindrical base part that is fixed in a cylindrical hole, which mouths in a surface via a mouth opening having an oval shape. 
   
   
       17 . A button bit of the type that is rotatable in a predetermined direction of rotation around a centre axis, the button bit comprising:
 a body having a front end surface and an envelope surface rearward of the front end surface; and   a number of spaced-apart peripheral buttons each positioned in a hole in the front end surface,   wherein the buttons protrude forward from the front end surface, and   wherein at least one individual peripheral button is tilted partly in relation to a centre axis of the bit, and partly in a forward direction of rotation in relation to a surface from which the button protrudes.   
   
   
       18 . The button bit according to  claim 17 , wherein a centre plane is defined by a plane orientated perpendicularly to the surface from which the button protrudes and intersects a mouth of the hole for the button at a point halfway between a rotationally leading end point along the hole edge and a rotationally trailing end point along the hole edge, and wherein a mass of material of the button situated rotationally in front of the centre plane is greater than a mass of material of the button situated rotationally behind the centre plane. 
   
   
       19 . The button bit according to  claim 18 , wherein a centre axis of the individual peripheral button is tilted at a primary tip angle (α) in relation to the centre axis of the bit, and wherein the centre axis of the individual peripheral button is tilted at a secondary tip angle (ε) in relation to the centre plane. 
   
   
       20 . A button bit of the type that is rotatable in a predetermined direction of rotation around a centre axis, the button bit comprising:
 a body having a front end surface and an envelope surface rearward of the front end surface; and   a number of spaced-apart peripheral buttons each positioned in a hole in the front end surface,   wherein the buttons protrude forward from the front end surface,   wherein at least one individual peripheral button is tilted partly in relation to a centre axis of the bit, and partly in a forward direction of rotation in relation to a surface from which the button protrudes,   wherein the buttons have an apex at a first end, the first end exposed when mounted in the hole, and   wherein a first generatrix from the apex to a rotationally leading end point along the hole edge has a first length and a second generatrix from the apex to a rotationally trailing end point along the hole edge has a second length, and the first length is less than the second length.   
   
   
       21 . The button bit according to  claim 20 , wherein a mouth of the hole for the individual peripheral button includes a countersunk entering surface, and
 wherein the countersunk entering surface extends perpendicularly to a centre axis of the hole.