Cutting by use of rotating axially moving tool – With means to apply transient – fluent medium to work or product – Including tool with duct
Reexamination Certificate
2002-07-03
2003-09-30
Howell, Daniel W. (Department: 3722)
Cutting by use of rotating axially moving tool
With means to apply transient, fluent medium to work or product
Including tool with duct
C407S048000, C408S230000, C408S233000, C408S713000
Reexamination Certificate
active
06626614
ABSTRACT:
TECHNICAL FIELD TO WHICH THE INVENTION BELONGS
This invention relates to a throwaway cutting tool such as a throwaway rotary cutting tool e.g. a drill or a throwaway tool. The throwaway cutting tools used here mean head exchangeable tools but include a type of tools in which a cutting edge formed on the cutting head is reground and the cutting head is changed when such regrinding becomes impossible.
PRIOR ART
Among known throwaway rotary cutting tools, there is one disclosed in JP patent publication 11-504269. With the cutting tool of this publication, a cutting head (cutting portion) having a cutting edge is detachably coupled to the tip of a tool body having a shank by applying a clamping force with a pull rod to allow regeneration of functions by replacing the cutting head. Protrusions and recesses are formed opposite to each other on the front surface of the tool body and a support surface of the cutting head to be brought into abutment with the former surface to obtain a wedging effect, and the protrusions and recesses are fitted together to transmit torque, and also to increase the clamping force between the tool body and the cutting head when the thrust force applied to the tool increases.
Besides, there is one in which, as in JP patent publication 2001-503683, protrusions and recesses for fitting are provided in an X arrangement on two imaginary lines that intersect at an acute angle on the center of rotation.
Problems the Invention Intends to Solve
With the tool disclosed in JP patent publication 11-504269, since the directions of the protrusions and recesses provided on the front surface of the tool body and the support surface of the cutting head are unified in one direction, torque transmission during cutting is done only through some of the protrusions and recesses, so that stress concentration occurs at such some of the protrusions and recesses. Thus, endurance problem tends to occur particularly during high-load cutting.
Also, dimensions of the cutting head made of cemented carbide (pitch of the protrusions and recesses provided on the support surface) vary due to delicate change in shrinkage factor due to variations in the sintering conditions, so that adhesion of the cutting head to the tool body worsens. This will worsen runout accuracy during setting and thus have a bad influence on the machining accuracy and cutting performance.
Further, in machining an oblique hole with a drill, lateral load is applied to the cutting head. By bearing this load on the pull rod, the cutting head is prevented from moving. But since the pull rod is at the center of rotation, which is apart from the load-application point (outer periphery) on the cutting head, the moment applied to the pull rod increases. Besides, since the pull rod has a long length and the absolute amount of elongation tends to increase due to pulling, when it is subjected to a lateral load, the pull rod is drawn, so that fixing of the cutting head becomes unstable, which may lead to chipping of the cutting edge.
In contrast, with the tool of the JP patent publication 2001-503683, since the protrusions and recesses are provided on the imaginary lines in a cross arrangement with reference to the central axis of rotation, lowering of the fitting accuracy due to dimensional change resulting from unbalanced transmission of cutting torque or heat shrinkage decreases compared with the above-described prior art. But since the protrusions and recesses are simple and small in number, reliability of torque transmission and durability are insufficient. Also, since coupling is done by means of a pull rod, rigid fixation of the cutting head cannot be desired.
With cutting tools used with workpieces rotating, such as boring bars, there are ones in which a cutting head (cutter tip) is mounted to the tip of a tool body (shank) by protrusion-to-recess fitting, as in German patent No. 3448086.
Among these tools, there are ones in which V-fitting recesses and protrusions are provided at three locations in a radial arrangement to clamp the cutting head with six surfaces. But this cannot insure centering accuracy and clamp stability unless the fitting surfaces are finished with high accuracy. Also, since the cutting force is borne at three locations, the recesses and protrusions tend to be fatigued or damaged. On the other hand, there are ones in which one square shaft and one square hole are formed at the axial portion and fitted together. But some clearance is left between the square shaft and the square hole, so that the cutting head (insert) tends to move by the cutting force by an amount of the clearance, so that the cutting edge tends to chip.
Means to Solve the Problems
In order to solve the above problems, according to this invention, a plurality of protrusions and recesses extending from the center of the tool toward its outer periphery and having V-shaped sections are provided radially and alternately with each other on a front surface of the tool body and a support surface of the cutting head which is brought into abutment with the front surface. Also, the protrusions have their height gradually increasing and the recesses have their depth gradually increasing from the center of the tool toward its outer periphery.
With a tool having a sufficient space, the cutting head is fixed by two bolts. Specifically, the cutting head is formed with two bolt holes with seats that are parallel to the axis so as to extend from the front surface of the cutting head through the support surface thereof on both sides of the center of the tool of the cutting head, and the cutting head is clamped to the tool body by bolts inserted through the bolt holes.
With a tool having an oil hole such as a drill, an oil hole is provided in the tool body and the cutting head at the center thereof so as to branch in the cutting head and the branched portions of the oil hole communicate with the bolt holes with the outlets of the branched portions of the oil hole formed by the inlets of the bolt holes.
With a tool having in its outer periphery two helical flutes that are symmetrical with respect to the center, an oil hole is formed in the tool body and the oil hole extends through the axis of the tool body and branches in a V-shape in the tool body. Branched portions of the oil hole open to the intersection of the front surface and outer peripheral surface of the tool body near a heel, and oil grooves opening to the helical flutes are formed in the outer periphery of the cutting head by cutting out the heel so as to communicate with the outlets of the branched portions of the oil holes.
With a tool having no cutting edge at the center of the tip, the cutting head may be fixed to the tool body with a single clamping screw passed through the center of the cutting head. For a small-diameter tool, which has little room for the space, this structure is suitable.
Besides, for a tool having at least the cutting head formed of a sintered material, the sintered skin on the engaging protrusions on the cutting head may remain without being removed.
This invention is also applicable to a gun drill for forming deep holes. In this case, a tool body is formed which has a section perpendicular to the axis that is a ¾ circle and a straight groove in its outer periphery and a plurality of protrusions and recesses of V-shaped section extending from the center of the drill toward its outer periphery are provided radially and alternately with each other on a front surface of the tool body and a support surface of the cutting head. The protrusions have their height gradually increasing and the recesses have their depth gradually increasing from the center of the drill toward its outer periphery. The protrusions and the recesses are arranged radially and have their height and depth varying in a radial direction.
With the throwaway gun drill, a fixing bolt formed with an oil hole along its axis is inserted into a bolt hole with a seat formed in the cutting head at a position offset from the axis of the cutting head and tightened into the support member to couple the cu
Greenblum & Bernstein P.L.C.
Howell Daniel W.
Sumitomo Electric Industries Ltd.
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