US 2903921 A
Description (OCR text may contain errors)
R. w. ANDREASSON 2,903,921
DRILL Filed. Oct. 9, 1957 Sept. 15, 1959 INVENTOR.
RQDOIF M ANOR'fiSSO/V A TTORA/f Y3 DRILL Rudolf .w. Andreasson, Birmingham, Mich.
Application October 9, 1957, Serial No. 689,128 11 Claims. (Cl. 77-68) This invention relates to a drill.
It is an object of the invention to provide a tube-formed drill of the type in which a tube is straight-fluted and twisted to give the proper helical formation; reference is made to my application, Serial No. 668,960 on an Oil Tube Drill, filed July 1, 1957 in which the method .of forming this type of drill shank is explained in detail.
It is an object of the present invention to improve on the previously disclosed drill in the formation of a tip for such drill.
As has been known, a twisted drill of this type can only be used on soft materials unless a hard tip of some kind is fastened to the drilling end. In the absence of such a tip, a tube-formed drill has a tendency to open up at the center due to the wedging action 10f chips'and the torque forces on the drill. It has been customary to braze on a solid tip drill and in some way to connect up the flutes of the tip with the flutes of the drill. The interior passages for coolant are also either opened to the outside of the tip or the tip is drilled to register with these passages. I
I have discovered that this type of oil tube drill can very easily be provided with a suitable drill tip by slotting the formed shank in a particular way and inserting in said slot a specially shaped pellet of hard material such as high speed steel or carbide. 1
Other objects and features of the invention relating to details of construction and operation will be apparent in the following description and claims.
Drawings accompany the disclosure and the various views thereof may be briefly described as:
Figure l, a side elevation of a completed drill.
Figure 2, a view of the tube from which the drill is formed.
Figure 3, a view of the straight-fluted tube.
Figure 4, a view of the twisted tube.
Figure 5, a sectional view of the drill.
Figure 6, a perspective view of the tip.
Figure 7, an illustration of the end of the tube prior to assembly of the tip.
Figure 8, a side view of the completed drill showing the side edge of the tip in elevation.
Figure 9, an end view of the completed drill.
Referring to the drawings:
The drill is formed from a tube 30 of carbon or chrome steel such as a 41-30 steel, which has proved quite satisfactory. The tube is shaped and fluted to provide straight flutes 32 and side lands 34 and also coolant openings 36 and 38. The tube is then twisted as shown in Figure 4. It is desirable then to coat the tube with a hard material such as chromium as shown in Figure 5 Where the coating 40 is shown to have substantial thickness relative to the wall of the tube.
These tubes vary in wall thickness, depending on the diameter of the tube utilized. The following table shows the relationship of the diameter to the wall thickness of the tube.
nited States Patent 0 ICC . 2 Diameter of tube (inches) Wall thickness in inches 1;, I .035 5, I p .035 l .049 K 0 I I .049 A .058 be .065 /8 .072
In order to strengthen the tube against bending and torsional distortion, it has been discovered, as described in my previously identified application, that it is possible to coat the tube with a relatively thick coating of hard material such as that described in the United States patent to Cole 2,694,647, issued November 16, 1944, or by another coating which is known to the 'trade as Colmonoy coating.
Also a chromium coating will accomplish this purpose, not of the thin variety such asis used for wear purposes or for an attractive finish, but a chromium coating of substantial thickness ranging about 20 to 30 percent of the wall thickness. For example, a quarter inch tube having a wall thickness of .035 inch would have a coating of about .009 inch chromium plate. A inch tube, vhaving a wall thickness of .072, would have a pref erably plate coating of about .018 inch. I
This coating has been found to provide a surprisin resistance to bending and torsional unwrapping of the drill and also has other advantages in that the molecular adhesionbetweenthe coating and the surface of the drill provides a useful sheath which stabilizes the entire drill,
' With a solid heat'treated drill if there is a breakage,-
there is a tendency for the parts to fragmentize fly 'through' the air and thus create a hazard to an operator.
The drill formed from tubestock will not fracture in this way. It isunnecessary to heattreatthe drill and of course the chromium plating, in addition to strengthening the device to make it practical as a drill, also provides wear surface. I 1 I When the drill is formed, the diameter is squeezed down below the fini'sh'diameter; for example, .018 inch for a quarter inch drill and then thisdimensionis Inade np by the plate coating. i'
The tip construction of the present invention is illustrated in Figures 1, 6, 8 and 9.
In the present simplified construction, I have found that I can provide a slot 46 in the end of avtwisted tube diametrically between the flutes leaving a portion of the openings 36 and 38 on each side of the slot 46. Each swirl or land then projects upwardly in spaced relation with the coolant opening being laid bare axially of the drill. The base of the slot 46 is preferably angled as shown at 48 to avoid a sharp corner and to leave more metal for the strengthening of the projecting portions of the drill. The slot 46 is provided to receive a small pellet 50 of tool steel or preferably tungsten carbide, this pellet having a crowned portion 52 to complement the surfaces 48 of the slot 46. The sides 54 and 56 of the pellet 50 are flat surfaces to engage and close in the openings 36 and 38. The sides 58 and 60 of the pellet 40 are flared to provide a proper cutting angle, and the end of the pellet is angled at 62 to provide the necessary point.
The angled base of the slot is provided not only to avoid sharp corners which might cause fracturing, but also to strengthen the bifurcate lands of the drill. These angled surfaces also increase the braze area and cause the drill load axially to resist the shearing force on the angled braze area.
The pellet is preferably brazed into the slot 46 to provide cutting edges 64 and 66 suitably spaced from the periphery of the drill. It will be seen that the coolant 3 passages 36 and 38 are slightly ensmalled by the cutting of the slot 46 and the insertion of the pellet 50. Nevertheless, each terminates on an opposite side of the cutting insert in close proximity to the cutting edges ,and coolant may flow through these passages with no further machining required.
The construction of thedrill is well suited to drills of original manufacture but also is readily used for re sharpening these drills. The ends may be cut off and slotted'forthe application of new tips.
' i What is claimed is as follows:
1. A 'drill'formed of a fluted and twisted tube, having coolant --.passages in spiral lands separated from each othenbyeach flute of the tool, the end of said fluted and twisted tube being opened at said passages on opposite sides of the center of said tool, .a slot formed diametrically ofsaid tube removing a'central portion thereof and opening said passages axially of the tube at the walls of said -slot,-and an insert of cutting material in said slot extending beyond said tube wherein said passages open onrtozathe outer :walls of said insert, and cutting edges provided on .the end of said insertprojecting from said slot.
. ,2. .A device as defined in claim 1 in which the base of the :slot is formed of walls converging from the side walls of the slot, and the base of the insert is shaped to compl ment thebase of said slot.
3. A drill formed of a fluted and twisted tube having interior coolant passages in spiral lands spaced on each side of the center, :the ends of the formed tube being hifurcate to leave the. lands projecting axially and lying on pppositesides .ofspaced, parallel planes, the ends of said coolant-passages opening at-the inside of said spaced lands and :at the. ,end of the lands, and a drill tip insert fastened insaidatube betweensaid bifurcate ends to fill the space .therebetween and projecting beyond said tube axially and radially, the opposite sides of the tip being open tos id passages at the ends of the lands.
,4. A drill as defined in claim 3 in which the inner walls of the bifurcate lands are spaced apart, each wall being interrupted axially by the open coolant grooves which terminate at the end of the lands, said insert also having surfaces to block the axial extent of the coolant groove openings.
5. 'Adrill as defined in claim '3 in which the tube is 4 formed of relatively tough metal and a coating of hard material molecularly bonded to said drill to create resistance to bending and torsional distortion.
6. A drill as defined in claim 5 in which the coating has a thickness of about 20 to 30% of the wall thickness of the tube.
7. A drill as defined in claim 6 in which the coating consists of a plating of hard metal.
8. A fluid cooled drill comprising a fluted shank including intertwined hollow spiral flutes having coolant passages, the flutes being connected by a solid web, one end of said shank constituting a working end, and the opposite end constituting a holding-end, the working-end terminating in a plane transverse to the axis, the hollow flutes being spaced at said working-end, to provide diametrically spaced openings, a cross passage in said working-end extending axially into said shank eliminating the connecting web and an inside portion of each flute to intersect the coolant passages axially along said passages, and a cutting element aflixed in said cross-passage having opposite faces closing axially said flute passages in the respective flutes-and dimensioned to project beyond said flutes of said working-end to provide cutting edges for I said drill.
9. A drill .as defined in claim 8 in which the opposed faces of said cutting element in contact with a flute liein parallel planes, the remaining faces of the opposed sides flaring outwardly to cutting edges.
10. A drill as defined in claim 8 in which the base surfaces of the cross-passage and of the cutting element are formed by axially and radially inwardly converging surfaces.
11. A drill as defined in claim 8 in which the drill shank is formed of a tube of relatively tough metal and said shank is coated with a hard material molecularly bonded to the outer walls thereof in substantial thickness to create resistance to bending and torsional distortion.
References Cited in the file of this patent UNITED STATES PATENTS Re. 19,182 Emmlons May 29, 1934 2,405,298 Fleischer Aug. 6, 1946 2,698,810 Staulfer June 4, .1955 2,817,983 Mossberg Dec. 31, 1957