US 2348874 A
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Description (OCR text may contain errors)
May 16, 1944. R, w. ANDi QEASSON 2,343,874 L I OIL HOLE DRILL- Filed March 22, 1945 IN'VE'NTOR 7? udbif M Had/2. 455 12 B v Y I ATTORNEYS.
Patented May 16, 1944 UNITED STATES PATENT OFFICE OILHOLE DRILL Rudolf W. Andreasson, Detroit, Mich. Application March 22, 1943, Serial No. 480,001
This invention relates to oil hole twist drills and has for its principal object the provision of a drill of this type capable of drilling relatively deep holes without becoming plugged by chips between the drill and the hole.
Objects of the invention include the provision of an oil hole drill so constructed and arranged as to insure an adequate flow of oil or other lubricant or coolant liquid at all times from the point of the drill along the flutes thereof, whereby to insure the chips formed by the drilling operation being carried away, thereby reducing the danger of breakage of the drill because of the accumulation of chips within the fiutesof the drill adjacent the point thereof; the provision of a drill of the type described so constructed and arranged as to prevent chips from becoming wedged in the relief of the lands of the drill; the provision of a drill of the type described in which the lands of the drill are relieved between the opposite side edges of the lands only whereby to provide at least four angularly spaced points of contact between the drill and the bore in which it is operating at any cross-section oi? the drill within such hole, the oil hole for each land being so constructed and arranged as to prevent chips from entering such relief; and the provision of an oil hole drill as above described in which the oil hole opens upon both the pointed end of the drill and upon the lands of the drill adjacent the point thereof.
The above being among the objects of the present invention the same consists in certain novel details of construction and combinations of parts to be hereinafter described with reference to the accompanying drawing, and then claimed, having the above and other objects in view.
In the accompanying drawing which illustrates a suitable embodiment of the present invention and in which like numerals refer to like parts throughout the several different views,
Fig. 1 is a partially broken, partially sectioned side elevational View of my improved drill;
Fig. 2 is a fragmentary view of the point end of the drill shown in Fig. l but rotated approximately 90 degrees about its axis from the position shown in Fig. 1 and taken looking in the,
direction of the arrows 2-2. of Fig. 1;
Fig. 3 is an enlarged cross-sectional view taken on the line 33 of Fig. 1;
Fig. i is an. enlarged cross-sectional view taken on the line 4-4 of Fig. 1'; and,
Fig. 5 is an enlarged, fragmentary sectional view taken on the line 5-=5 of Fig. 1 and "passing clearly disclose the details of construction thereof.
Oil hole twist drills are commonly used insocalled deep drilling operations, that is, where the depth of the hole to be drilled is several times that of the diameter of the drill, and the purpose of the oil or other liquid is to both provide liquid which will enhance the ease of the cutting operation and to carry the chips away from the point of the drill up the flutes and discharge them from the hole being bored. An oil hole is usually provided beneath the surface of each land of the drill and extends from the shank thereof to the pointed end of the drill where it opens onto such. end immediately behind the adjacent cutting edge. the shank of the tool and such bore is suitably connected to a source of the desired liquid maintained under a suitable pressure.
It has been found that even with oil hole drills, and particularly where a, relatively deep hole is being drilled, the chips cut by the drill have a tendency to pile up and pack together in the flutes near the point of the drill, with the result that it often occurs that unless the drill is removed from the hole one or more times during drilling operation the drill may become stuck in the work and twisted ofi. One reason why, in oil hole drills as heretofore constructed, the liquid discharged through the oil holes has not carried such chips up the flutes and prevented such paclzi'ng is that the chips are seldom small enough to block the body relief on the land and when the flutes tend to become blocked with chips the liquid llows up the drill along this relief, instead of be" ing forced through the flutes proper so as to free the flutes of the chips.
In oil hole drills as heretofore constructed there has been nothing which tends to stop the flow of the liquid from the oil holes along the body relief rather than along the flutes. j I In accordance with the present invention oil hole drill is provided that is so constructed and arranged as to substantially prevent any flow. or? the liquid discharged from the oil holes along body relief of the drill, the liquid being forced to flow back along the drill in the flutes thereof. It has been found that by forcing substantially all of the liquid discharged through the oil holes to thepoint of a drill backward along the drill in the flutes and preventing a substantial flow there-- of in the body reliefs of the drill, the chips are carried away from the point of the drill and are prevented from packing up in the flutes, in a much centra 'lyt ugh the oil hole at such end, to more more eflicient manner than with drills as her-es The oil holes open into a larger bare in tofore provided, not only resulting in faster cutting operations, particularly in View of the fact that it is seldom necessary to withdraw the drill from the holes during the drilling operation, but also providing a construction in which there is considerably less tendency for the drill to break.
In accordance with the present invention, instead of providing a body relief extending from a point spaced from the leading edge of each land clear across such land and including the trailing edge thereof, such relief is terminated short of the trailing edge of each land so as to provide each land with two lines of contact between it and the bore being drilled. This is done for two reasons. The first reason is that with a two flute drill, for instance, every increment of length of the fluted portion of the drill is provided with four points of contact with the bore being drilled and each point of contact is angularly spaced about the axis of the drill from the next. This prevents the point of the drill from attempting to climb sideways on the side of the bore when the outer edge of the point of the drill tends to dig into such surface, and thus prevents the occurrence of a condition which occurs with usual types of drills and which often results in breakage of the drill. The second reason is that it segregates the body clearances of the drill from the flutes of thedrill and this is the most important point as far as the present invention is concerned.
Additionally, in accordance with the present invention, those ends of the oil holes adjacent the point of the drill are opened onto the side surface of the drill within the area of the corresponding body reliefs. While the extent of such opening of the oil holes onto the reliefs may be varied to a greater or lesser extent, it is preferably opened onto the reliefs for a distance axially of the drill approximately equal to the diameter of the drill. This means that the oil or other liquid being forced through the oil holes during a drilling operation flows outwardly into the body reliefs adjacent the point of the drill between the body reliefs and the wall of the bore being drilled, as it is being directed toward the point of the drill.
As a result of the above described construction and because of the kinetic energy of the flow of such liquid, it tends to prevent such liquid from flowing back up the body relief, and because the body relief is sealed from the adjacent flutes as previously described such liquid is forced to the point of the drill and its only path of escape is back along the flutes. This insures a much stronger flow of liquid along the flutes than in the prior types of such drills with the result that the chips are washed away from the point of the drill and up the flute in a much more eificient manner than in prior constructions and thereby eliminates the primary disadvantage of previous constructions. Tests show that drills constructed in accordance with the present invention are capable of drilling relatively deep holes at a faster rate of rotation and at a faster feed than oil hole drills of conventional constructions and seldom if ever require the drills to be removed from the hole being bored during a drilling operation in order to insure removal of the chips. Furthermore, drills constructed in accordance with the present invention show a considerably less tendency to break and the number of breakages is considerably less than in drills of conventional constructions. 7
In the broader aspects of the invention it will be appreciated that it is applicable to twist drills having either a straight, tapered or other types of shank, and regardless of the number of flutes. However, for the purpose of illustration the drill shown in the drawing is of a conventional type having a cylindrical shank I0 and a main body portion indicated generally at I2 of the conventional two flute type. The flutes which are illustrated at I4 are of the conventional helical type diametrically opposed to each other with respect to the axis of the drill. In accordance with the present invention the lands between the flutes I4 are'relieved as at I6 to provide a body relief but such relief I6 terminates short of the side margins of the lands so as to provide outstanding ribs or beads I8 lying within the circle of the normal diameter of the drill. The depth of the reliefs I6 may be conventional, that is from 0.005" to 0.015" for the most commonly used sizes of drills. It may be noted, however, that the ribs or beads I8 on the trailing sides of the lands may lie a small distance, for instance, 0.001 to 0.003", inside of the full diameter circle of the drill, and the trailing portion of the rib or bead I8 on the leading side of each land in the direction of rotation may be back off as at 20, as indicated in Figs. 3 and 4, if desired, to provide a lateral cutting edge extending the full length of the fluted portion of the drill in accordance with some conventional practices. The end of the drill opposite the shank III is, of course, ground to provide the usual point providing cutting edges 22.
As brought out in Fig. 1 the shank II] is provided with a relatively large central bore 30 which lies in open communication with a pair of oil holes 32. Each oil hole 32 extend downwardly in straight relation with respect to the axis of the drill to the fluted portion of the drill and within the latter it is arranged in the same helix as the flutes I4. Each oil hole 32 within the fluted portion of the drill lies below the surface, and preferably approximately centrally, of the corresponding land of the drill. Each oil hole 32 extends, of course, clear to the point of the drill and opening onto the point end of the drill rearwardly of the corresponding cutting edge 22.
The particular manner in which the oil holes 32 are formed in the drill is of no importance as far as the present invention is concerned and may thus be formed in any suitable or conventional manner. For instance, in accordance with one conventional method of making such drills the flutes I4 may be milled or otherwise formed straightand in parallel relation to the axis of the drill and the oil hole drills 32 simply drilled through the length of the drill in the correspond,- ing land portions thereof, after which the fluted portion of the drill may be twisted to the desired helix. On the other hand the oil holes 32 may be formed as, for instance, as shown and described in my United States Letters Patent Nos. 2,290,933 and 2,290,934, in which case the oil holes are initially formed as grooves opening onto the outer face of the main body portion of the drill, the grooves are each connected to the bore 39 by a drilled hole, and then the open sides of the grooves are suitably closed. It will be appreciated, of course, that in any event the oil or'other liquid which is to be fed through the oil holes 32 to the point of the drillis introduced under suitable pressure into the bore 30 from which it flows through the oil holes. 32 to the pointed end of the drill.-, l
In accordance with the present invention, instead of projecting-the'oil holes 32 as entirely closed passages from the bore 30 completely'to the point of the drill, each oil hole at and adjacent the point of the drill is opened up from the pointed end of the drill onto the peripheral portion of the drill by means of a slot 34 which, as best brought out in Fig. 4, is located in the corresponding land of the drill between'the ridges or beads I8 at opposite sides of such land. The slots 34 may be formed by a milling operation before the drill has been hardened or by a grinding operation after the drill has been hardened, the latter operation being necessarily employed to extend the slots as the pointed end of the drill is worn away in sharpening. The length of the slots 34 may, of course, vary to a greater or lesser extent but they are preferably of a length equal to 25% to 150% of the diameter of the drill and more preferably equal to the diameter of the drill.
With the construction thus described it will be appreciated that during a drilling operation when a liquid is being forced through the oil holes 32, when it reaches the slotted end portion of the drill the liquid will flow out through the slots 34 to the periphery of the drill as well as continue to flow toward the point of the drill. Because of the beads or ridges l8 on each side of the slots 34 such liquid will be prevented from flowing laterally and directly into the adjacent flutes M and, because of the kinetic energy of the flow of such liquid, it will be forced lengthwise of the drill toward the point of the same immediately behind the associated cutting edge 22. After reaching the cutting edge 22 it cannot flow back up the drill in the associated relief It for the reason that the flow of liquid in such relief is toward the point of the drill and thus prevents such counter-flow and, accordingly, its only avenue of escape of the liquid discharged from each oil hole 32 is to the flute l4 immediately following the same. The liquid thus flows up such flute and is prevented by the ridges or beads Hi from flowing into the relief I6 upwardly from the point, at least in a material volume, and thus is constrained to flow up the flutes, carrying the chips that have been cut from the work by the cutting edges 22 upwardly and out of the hole therewith. It has been found that this action is extremely efiective inpreventing the building up of a quantity of chips in the flutes adjacent the point of the drill and thus prevents such chips from jamming between the drill and the bore of the hole being drilled and thus offering a sufficient resistance to rotation of the drill to break it as so often occurs with drills of conventional construction. This very fact makes it unnecessary in substantially all cases to withdraw the drill occasionally from a hole during the operation of drilling the same to insure clearing the hole of an accumulation of chips, and permits the drill to be operated at a higher rotational speed and at a greater rate of feed than has heretofore been found practically possible with drills of conventional constructions.
Having thus described my invention what I claim by Letters Patent is:
1. A drill comprising, in combination, a generally cylindrical body portion having flutes formed therein providing lands between said flutes, said lands being relieved between the opposite edges thereof to provide outstanding ridges along each edge thereof, each of said lands having an oil hole therein extending longitudinally thereof and opening onto the point of said drill, and said oil holes being open laterally to the relief of the corresponding lands adjacent said point of said drill only,
2. An oil hole drill comprising, in combination, a main body portion having flutes therein and lands between said flutes, said lands being radially relieved from a point circumferentially spaced from one edge thereof to a point circumferentially spaced from the opposite edge thereof, said lands each being provided with an oil hole therein below the surface thereof and opening onto the point end of said drill, and said lands at the point end only of said drill being slotted within the relieved area thereof into said oil holes whereby to permit liquid flowing through said oil holes to flow radially outwardly as well as axially of said drill at said point end thereof.
3. A spiral twist drill having an oil hole located therein below the surface of each land thereof, the lands of said drill being centrally relieved between and short of the opposite side margins of the lands thereof over the length of said lands, and said lands being slotted longitudinally thereof into said oil holes from the point end of said drill toward the shank end of said drill for a distance equal to twenty-five percent to one hundred and fifty percent of the diameter of said drill.
4. A oil hole drill comprising a main body portion and a shank, said main body portion being provided with spiral flutes therein and lands between said flutes, that end of said main body portion opposite said shank being pointed, an oil hole in said main body portion below the surface of each of said lands and opening onto said pointed end of said drill, said lands being radially relieved between and short of the opposite side edges thereof, and that end of said main body portion adjacent said pointed end thereof being slotted longitudinally of and between the side edges of said lands so as to open said oil holes to the surface of said main body portion within the relieved portions of said lands, said slots extending from said pointed end of said main body portion toward said shank of said drill for a distance equal to twenty-five percent to one hundred and fifty percent of the diameter of said drill.
5. An oil hole drill comprising a main body portion and a shank, said main body portion being provided with spiral flutes therein and lands between said flutes, that end of said main body portion opposite said shank being pointed, an oil hole in said main body portion below the surface of each of said lands and opening onto said pointed end of said drill, said lands being radially relieved between and short of the opposite side edges thereof, and that end of said main body portion adjacent said pointed end thereof being slotted longitudinally of and between the side edges of said lands so as to open said oil holes to the surface of said main body portion within the relieved portions of said lands, said slots extending from said pointed end of said main body portion toward said shank of said drill for a distance approximately equal to the diameter of said drill.
RUDOLF W. ANDREASSON.