Rotary Tool and Guide

This invention relates generally to a drill and more specifically to improvements in a drill having indexable cutting inserts. The drill is of the type shown in U.S. Pat. No. 3,963,365.

Previously available drills of the aforementioned type include indexable inserts to increase the useful life of the drill. The drill commonly is equipped with wear strips to guide the drill for axial movement in substantially a straight line and to prevent the steel body from rubbing against and being worn by the wall of the hole being drilled. In U.S. Pat. No. 4,149,821, such wear strips are eliminated by offsetting the inserts at a particular angular relationship to radially balance the drill.

Drills of the type discussed in the aforementioned U.S. Patents often experience a relatively short service life when drilling hard metals, as metal chips become lodged between the outermost periphery of the drill and the inside of the bore, particularly when the drill is rotated about an upright axis. As friction heats the drill to red-hot temperatures, the chip binding problem becomes more acute. The individual drills are expensive, and the incidences of early drill failure significantly increase the average fabricating cost of a workpiece

It is therefore a general object of the present invention to provide an improved indexable drill. It is a further object to provide such a drill which is highly stabilized in the direction of feed and which provides improved chip removal.

It is still another object of the invention to provide such a drill which has improved chip flow characteristics and which is not subject to frequent binding in the bore caused by chips lodging between the periphery of the drill and the bore surface. It is another object to provide such a drill wherein such binding is reduced even when the drill is rotated about a vertical axis.

It is a further object of the invention to provide a drill of the aforementioned type which is stabilized in the axial direction so as not to require wear strips or modification of the angular relationship between the inserts. It is yet another object to provide such a drill which can accurately locate and start a hole without requiring a pilot hole.

It is a further object of the invention to provide an indexable drill which obviates very rigid spindles to stabilize the tool during drilling.

It is still a further object of the invention to provide a drill which accommodates high drill rates on conventional machines, better tool life and a reduction of the need for sharpening.

In accordance with the above objects the drill of the present invention has a straight fluted end with increased chip clearance. The chip removal recesses have substantially axial planar surfaces rather than inclined surfaces adjacent the inserts to thereby cause the chips to flow axially rearwardly with less tendency to lodge between the drill and the surface of the bore. The chips flow rearwardly until they contact a rearward portion of the flute where they are directed outwardly above the bore. The chip clearance and flute construction, and a decreased clearance between the outer periphery of the drill and the bore surface, prevent the chips from lodging between the surfaces of the drill and the bore. A grooved barrel adjacent the fluted end is received in a bushing which is part of the drill fixture. The bushing steadys the drill to eliminate need for wear strips. The bushing also permits the drill to be used on a less rigid machine spindle or head than would normally be necessary with a conventional tool. The fluted area is substantially straight and non-flared and tapers outwardly toward the grooved barrel so that the tool can be quickly and easily removed from the fixture. The tool lifetime is increased many times over that of a conventional drill with indexable inserts.

These and other objects, features and advantages of the present invention will become apparent to those skilled in the art from the description which follows and from the drawings.

FIG. 1 is a side view of a drill constructed in accordance with the present invention.

FIG. 2 is an end view of the drill of FIG. 1.

FIG. 3 is an enlarged view of the fluted end portion of the drill of the present invention.

FIG. 4 is an end view taken along lines 4--4 of FIG. 3.

FIG. 5 is a perspective view of the drill of FIG. 1 in its operating position in a drill assembly.

FIG. 6 is a view similar to FIG. 5 but with the drill advanced through the workpiece.

Referring now to FIG. 1, therein is shown an indexable drill 10 having a shank 12 and a straight fluted cutting end 14 with carbide inserts 16 and 17 fixed to the shank by screws 18 or other suitable conventional means.

The shank 12 tapers outwardlly from the straight fluted end 14 at approximately a 35 degree angle at 22 to a grooved body portion 24 having a diameter greater than that described by the outermost edge of the outermost insert 18. A conventional coolant collar 26 encircles the shank axially rearwardly of the grooved body portion 24. The axially rearwardmost portion of the shank 12 tapers radially inwardly at end or Morse taper 28.

The inserts 16 and 17, and the support structure in the fluted end 14 for the inserts are of conventional design, such as set forth in the aforementioned U.S. Pat. No 3,963,365, and so will not be described in further detail here. However, the outermost carbide insert 16 is supported in the end 14 so that the radially outermost cutting point 36 projects only slightly outwardly of the outermost surface of the fluted end 14. This distance of projection, represented by d in FIG. 3, is less than 0.005 inch and preferably is 0.004 inch. The dimension d is sufficient to prevent the fluted end from rubbing against the surface of the bore, and yet is small enough so that chips will not enter and lodge between the surface of the bore and the surface of the fluted end 14.

The fluted end 14 is constructed to provide increased chip clearance and improved chip flow to prevent binding. The fluted end 14 includes chip removal recesses indicated generally at 40 and 42 associated with the carbide inserts 17 and 16, respectively. The recesses 40 and 42 extend generally axially rearwardly from the respective insert locations and are characterized by straight wall portions 46, 47 and 48, 49, all of which lie substantially along planes which are parallel to the axis of rotation of the drill. The straight walls 46, 47 and 48, 49 extending rearwardly from the respective inserts 17 and 16 reduce the tendency for the chips cut from the workpiece to angle toward periphery 52 of the fluted end 14. Instead, the chips are directed more in the axially rearwardly direction to reduce the possibility of binding between the periphery 52 and the wall of the bore. The chip removal recesses 40 and 42 taper outwardly toward the angle 22 at locations 54 and 55 (FIGS. 1 and 3) to direct chips outwardly from the bore. The tapers 54 and 55 are located a distance at least equal to the maximum depth of penetration of the drill 10 to permit free exit of the chips from the workpiece as the bore is being formed.

The grooved body portion 24 has a generally cylindrical surface of radius greater than the radius of the straight fluted end 14. A plurality of longitudinally extending grooves 60 are equally spaced around the periphery of the cylinder to permit cooling and lubricating fluid to flow axially toward the end 14. Six grooves 60 are shown in FIGS. 1 and 2 but more (FIGS. 3-6) or less may be provided depending on cooling and lubricating requirements. A conventional cooling fluid path 64 is formed within the drill 10 and communicates with the coolant collar 26. The coolant path 64 extends axially forwardly from the collar 26 to openings 66 (FIG. 2) adjacent the carbide inserts 16 and 17.

The Morse taper 28 is adapted for insertion into a conventional chuck assembly, such as shown at 70 in FIG. 5. In the preferred embodiment the workpiece to be drilled, indicated generally at 72, is rigidly supported in a fixture 74. The fixture 74 includes a lower base portion 76 having locating structure 77 for positioning the workpiece 72 in the proper location relative to the fixture 74. A bearing support block 78 is fixed securely with respect to the base portion 76 and is offset above the base portion to permit the workpiece 72 to be positioned therebetween. A drill guide bearing 82 is located in the support block 78 for axially receiving the grooved body portion 24. The diameter of guide bearing opening 84 is approximately equal to but slightly greater than the diameter of the grooved body portion 24 so that the drill can move axially within the bearing during the drilling operation. The bearing 82 provides lateral stability for the drill with respect to the workpiece 72 for precisely locating the bore without drilling a pilot hole in the workpiece and for preventing wobble that would result in an irregular bore. In the preferred embodiment the guide bearing 82 is a solid drill bushing within which the grooved body portion 24 rotates. Alternatively, the guide bearing 82 is a needle bearing having an inner sleeve 88 which rotates with the drill 10 to reduce friction between the drill and the fixture 74. A fixed bearing 82 provides slightly less wobble of the end 14 with respect to the workpiece 72. In the preferred embodiment, the difference between the inner diameter of the fixed bushing and the outer diameter of the grooved body portion 24 is less than 0.010 inch to prevent any substantial wobble. A difference of 0.008 inch has been found to work satisfactorily. A conduit 92 located adjacent the drill 10 provides a continuous supply of water and/or grease which flows downwardly through the grooves 60 to cool the drill 10 and to provide lubrication for the guide bearing 82, particularly when the bearing is a fixed rather than floating type.

The workpiece 72 is tightly secured with respect to the fixture 74 by the locating structure 77 as well as conventional clamping structure (not shown). The drill 10 is rotated at a suitable rate of speed, preferably about 700 rpm, and fluid is directed through the conduit 92 unto the grooved body portion 24. Fluid also is directed through a conduit 96 to the coolant collar 26 to the tip of the drill via the coolant path 64. The drill is advanced axially with respect to the fixture 74 and the workpiece 72 while being guided by the bearing 82 to a precise location on the workpiece 72. The end 14 is advanced through the workpiece 72 as chips cut by the carbide inserts 16 and 17 are directed upwardly through the staight walled chip removal recesses 40 and 42 and out the upper portion of the fluted end 14.

Having described the preferred embodiment, it will be apparent that modifications can be made without departing from the scope of the invention as defined in the accompanying claims.