Abstract:
A rotary cutting tool having a cutting insert slidably supported therein. The cutting insert is moveable from a retracted position to an extended position by means of a pressurized fluid which bears directly against the cutting insert.

Description:
FIELD OF THE INVENTION 
   The present invention relates to a rotary cutting tool having a cutting insert for deburring of bores. 
   BACKGROUND OF THE INVENTION 
   Such rotary cutting tools are known either in the form of stand alone tools for deburring ready made holes or in the form of drills having incorporated deburring capability. In both cases the deburring is generally performed by a spring-loaded cutting insert. However, there are situations in which there is not enough room for a spring. This can be the case for very small diameter cutting tools or in drills where it is required to locate the deburring insert in the vicinity of the drill&#39;s flutes. 
   U.S. Pat. No. 6,270,295 describes a cutting tool which utilizes pressurized fluid for indirectly loading a blade. In the &#39;295 patent, a piston  118  resides in a side conduit  112  and pressurized fluid, flowing in the side conduit  112 , assists in pushing the piston  118  against a cartridge  122  which holds a blade  126 . 
   SUMMARY OF THE INVENTION 
   In accordance with one aspect of the present invention, there is provided a rotary cutting tool having a longitudinal axis of rotation and comprising: 
   a conduit, for passage of fluid, formed in the cutting tool and extending generally axially, 
   an insert pocket opening out to a peripheral surface of the cutting tool via an aperture, the insert pocket communicating with the conduit, and 
   a cutting insert slidably retained in the insert pocket, the cutting insert being slidable from a retracted position to an extended position by means of fluid pressure applied by the fluid which bears against and biases the cutting insert towards the extended position, wherein in the extended position at least a portion of the cutting insert protrudes from the aperture beyond the peripheral surface of the cutting tool. 
   Preferably, a holding bore opens out to the peripheral surface and communicates with the insert pocket. 
   Typically, the cutting insert has an insert axis defining a back to front direction and a plane including the insert axis passes there through, the cutting insert comprising: 
   a body portion having a back surface at a back end of the body portion, and 
   a cutting portion at a front end of the body portion, the cutting portion having two cutting edges being reflection symmetric with respect to the plane. 
   Generally, the pressurized fluid bears directly against the back surface of the cutting insert. 
   Preferably, a holding member is located in the holding bore and abuts the cutting insert when the cutting insert is in the extended position. 
   If desired, the rotary cutting tool is a drill. 
   In another aspect, the present invention is directed to a rotary cutting tool having a longitudinal axis of rotation and comprising: 
   a conduit, for passage of fluid, formed in the cutting tool and extending generally axially, 
   an insert pocket opening out to a peripheral surface of the cutting tool via an aperture, the insert pocket communicating with the conduit, and 
   a cutting insert slidably retained in the insert pocket, the cutting insert being slidable from a retracted position to an extended position in which at least a portion of the cutting insert protrudes from the aperture beyond the peripheral surface of the cutting tool; wherein: 
   a back surface of the cutting insert is in communication with the conduit such that a fluid present in the conduit is capable of urging the cutting insert from the retracted position to the extended position, without the assistance of a spring. 
   Such a rotary cutting tool may be a drill. 
   In another aspect, the present invention is directed to employing such a drill in accordance with the present invention to drill a hole in a workpiece while passing fluid through the conduit such that said fluid applies pressure to the back surface of the cutting insert and causes the cutting insert to slide towards the extended position. The fluid may exit the drill through a minor portion of the conduit that extends outwardly, thereby cooling the workpiece. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a better understanding of the present invention and to show how the same may be carried out in practice, reference will now be made to the accompanying drawings, in which: 
       FIG. 1  is a partial first side view of a drill having a deburring mechanism in accordance with the present invention; 
       FIG. 2  is a partial second side view of the drill with its conduit and deburring mechanism shown in hidden lines; 
       FIG. 3  is a cross sectional view of the deburring mechanism taken along the line III-III in  FIG. 1 ; 
       FIG. 4  is similar to  FIG. 3  but with a cutting insert and holding member removed; 
       FIG. 5  is a perspective view the cutting insert in accordance with the present invention; and 
       FIG. 6  is a top view of the cutting insert shown in  FIG. 5 . 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
   Attention is first drawn to  FIG. 1 . The present invention will be described from herein with reference to a drill  10  however it will be clear to the skilled person in the art that it can be applicable to a variety of rotary cutting tools where deburring is required. The drill  10  has a longitudinal axis of rotation A defining a forward to rear direction and a cutting tip  12  located at a forward end thereof. Two flutes  14 , extending rearwardly from the cutting tip  12  along a peripheral surface  16  of the drill  10 , form two identical lands  18  therebetween. A deburring mechanism  20  in accordance with the present invention is formed on one of the lands  18  adjacent the cutting tip  12 . It should be noted that directional terms appearing throughout the specification and claims, e.g. “forward”, “rear”, “front”, “back”, etc., are used as terms of convenience to distinguish various surfaces relative to each other. Although these terms may be meaningful with reference to particular component orientations, they are used for illustrative purposes only, and are not intended to limit the scope of the appended claims. 
   Attention is additionally drawn to  FIG. 2 . A conduit  22  for the passage of fluid, having a main portion  24  and two minor portions  26 , is formed in the drill  10 . The main portion  24  extends forwardly along the axis of rotation A to a forward ending  28  adjacent the cutting tip  12 . Each minor portion  26  diverges forwardly and outwardly from the forward ending  28  to a respective land  18 . 
   The deburring mechanism  20  includes a holding bore  30 , a holding member  32  and a cutting insert  34  that is capable of lateral movement between a retracted position and an extended position in a generally cylindrical insert pocket  36 . As will be described in greater detail below, the cutting insert  34  is prevented from exiting the insert pocket  36  by means of the holding member  32 , and is loaded in the insert pocket  36  by means of fluid pressure which bears directly against the cutting insert  34  at one of its ends. 
   Attention is drawn to  FIGS. 4 to 6 . The insert pocket  36  communicates with the main portion  24  of the conduit  22  and opens out to the land  18  via an aperture  38 . The holding bore  30  is formed in the land  18  adjacent the insert pocket  36  and has a threaded portion  40  and a socket  42 . The socket  42  extends outwardly from the threaded portion  40  and opens out to the land  18 . 
   The cutting insert  34  has an insert axis B defining a front to back direction and comprises a generally cylindrical body portion  44  and a cutting portion  46 . The body portion  44  has a back surface  48  at a back end, a front surface  50  at a front end and a peripheral body surface  52  therebetween. A plane P which includes the insert axis B divides the cutting insert  34  into two sides. A holding recess  54  having a recess face  56  and a back face  58  is formed on the peripheral body surface  52 , on one side of the cutting insert  34 , and opens out to the front surface  50 . The recess face  56  has a concave arc shape in a cross section perpendicular to insert axis B and the back face  58  is located at a back end of the holding recess  54  and is perpendicular to the insert axis B. The cutting portion  46  has opposing flank surfaces  60  and a top surface  62  which all extend forwardly from the front surface  50  of the body portion  44  to an insert nose  64 . The flank surfaces  60  are located on opposing sides of the plane P. The top surface  62  bridges between the flank surfaces  60 , is generally perpendicular to the plane P and proximate to the insert axis B. The cutting portion  46  has two cutting edges  66  located each between the top surface  62  and a respective flank surface  60 . The cutting edges  66  are reflection symmetric with respect to the plane P and have each a rake surface  68  associated with the top surface  62  and a relief surface  70  associated with the respective flank surface  60 . 
   Attention is additionally drawn to  FIG. 3 . The cutting insert  34  is located in the insert pocket  36  with its back surface  48  facing inwardly. The holding member  32  has a screw portion  72  and a head  74  which are, respectively, threadingly received in the threaded portion  40  and located in the socket  42  of the holding bore  30 . The head  74  of the holding member  32  protrudes into the insert pocket  36  and, when the cutting insert  34  is in the extended position, abuts at least a portion of the back face  58  of the holding recess  54 . Rotation of the cutting insert  34  in a given direction around the insert axis B is limited in the insert pocket  36  by the head  74  of the holding member  32  abutting against the recess face  56  of the holding recess  54 . Loading of the cutting insert  34  in the insert pocket  36  is provided by fluid that flows through the conduit  22  and into the insert pocket  36 . 
   The fluid pressure that is formed in the insert pocket  36  bears against the back surface  48  of the cutting insert  34  forming a force which biases and urges the cutting insert  34  radially outwardly. In other words, the back surface  48  of the cutting insert  34  is in communication with the conduit  22  such that a fluid present in the conduit  22  is capable of urging the cutting insert from the retracted position to the extended position, without the assistance of a spring. After fluid passes through the main portion  24 , it exits through the minor portions  26 . Thus, one may use the present tool to drill a workpiece while passing fluid through the conduit  22  such that the fluid applies pressure to the back surface  48  of the cutting insert  34  and causes the cutting insert  34  to slide towards the extended position, the fluid exiting the drill through a minor portion  26  of the conduit that extends outwardly. The exiting fluid thus cools the workpiece in which a hole is being drilled and deburred. 
   A device in according with the present invention potentially provides a number of features. First, it may allow for biasing the deburring insert without complex mechanisms or springs. Second, the deburring insert can be incorporated in a drill in the vicinity of the drill&#39;s flutes. Third, the deburring insert can be incorporated in small diameter tools in which there is insufficient room for springs, or the like. Finally, the deburring insert may be loaded at the forward end of a drill to drill through holes and deburr both sides of the hole. 
   Although the present invention has been described to a certain degree of particularity, it should be understood that various alterations and modifications could be made without departing from the scope of the invention as hereinafter claimed.