Патент USA US2403861код для вставки
July 9, 1946. . w,- F, KLEMM ' ' CENTER DRILL ’ ‘ ' ‘2,403,861 ' Filed Dec. ,18, 1944 M‘ . v// l 1,15 l A? /¢| I _. _/ 3/6‘ ' ' - ” INVENTOR. ' I 577721717575. 2,403,861 Patented July 9, i946 ' UNITED ‘ STATE sPArENT oFFicET I 2,403,861 ‘ CENTElftHDRILQL William F. Kleinm, Detroit, Mich. Application December 18, 1944, Serial No. 568,634 7 3 Claims. - .. This invention relates to center drills and par ticularly to a center drill in which the cutting portion is formed on a continuous curve provid ing vertical relief for the end cutting edge of the pilot portion. (01. ‘ii-66) ' V 2 1 , ' , Heretofore center drills were provided with a ’ ‘abovethe end cutting edges and with side cutting edges which are disposed onva continuous curve .with the cutting edges on the countersinking por tion of the drill; to construct a center drill by grinding the side cutting edges on a true arc struck from' a center disposed above the end cutting edges of the pilot portion and providing radial re countersinking portion and apilot portion on the lief to the side cutting edges‘ and vertical relief, end of the body. The pilot portion was of con to the bottom cutting edges; andin general to ventional drill construction extending from the end of a frusto-conical countersinking portion 10 provide a center drill which is simple in con struction and economical of manufacture. _ which machined the hole drilled by the pilot to a desired taper. Difficulty was experienced when employing this type of center drill due to the small Other objects‘ and features of novelty of the invention will be speci?cally pointed out or will become apparent when referring, for a better pilot portion becoming heated and expanding in the hole causing it to become broken by the ap 15 understanding of the invention, to the following plied torque. When the break occurred across the small pilot ‘portion, it was di?icult to remove , description taken in conjunction with the accom panying drawing wherein the single figure dis closes a center drill embodying features of this the broken part because of its being wedged in invention and a workpiece having a center drilled the hole. Various attempts were made to con ' V struct center drills in some manner to overcome 20 thereby. A center jdrill I0 is illustrated having a body this dif?culty and some improved center drills portion II and a cutting portion I2. The cutting have resulted from this effort. portion is made up of a countersinking portion l3 In practicing the present invention, a center and a pilot portion M which blend into each other. drill is formed by constructing'the countersink ing and pilot portions in smooth continuous sec 25 Cutting edges l5 are provided in the countersink ing and pilot portions by the flutes l6 machined tions which blend with each other to have the side cutting edges disposed in smooth continuous therein to project into the body portion. curves. Preferably the curves are arcs of a circle struck from a center disposed above the ‘ cutting edges l5 are struck from an are I‘! about The a center 18 which is disposed above the end cut end of the pilot portion to have the cutting end’ 30 ting edges IQ of the drill section. The distance 2! above the bottom cutting edges IQ of the pilot of the pilot portion of greater diameter than the portion M is substantially equal to half the portion directly thereabove. This not only pro diameter 20 of the pilot portion, that is to say, vides a simple curve upon, which the side cutting substantially equal to its radius. The portion of edges are ground and relieved, but vertical relief the center drill disposed on the line 22 upon which is provided to the bottom cutting edges .of the the center [8 is located is of the smallest diam pilot portion. When the center drill becomes eter. The portions of the center drill above and heated during the operation, the body portion of below the line 22 are of increasingly larger the pilot portion cannot expand suf?ciently to diameters. engage the side of the hole cut by the end cut Relief is provided to the cutting edges I5 in ting edges, and breakage from this cause is ~10 the regular manner by tilting the tool toward eliminated. The relief above the end cutting the grinding element rearwardly of the cutting edge of the pilot portion is useful in providing edges as the grinding element is oscillated across chip clearance which permits the free movement the countersinking and pilot portions about the of the chips upwardly in the flutes of the portions. center l8. Vertical relief will be provided in the should the pilot portion become broken, the hole 23 cut by the pilot portion the same dis clearance above the bottom cutting edges permits tance above the line 22 that the end cutting edges the broken end to be easily removed from the l9 are disposed below the line. This vertical drilled hole. ' ‘ clearance above the end cutting edges is pre Accordingly, the main objects of the invention vents the heat generated in the. cutting portions are: to provide a center drill with cutting por of the center drill from expanding the pilot por tions having the side cutting edges disposed in smooth curves; to provide a center drill with tion a sufficient amount to cause it to bind within countersinking and pilot portions which blend the hole. The ‘breakage which normally occurs due to the expansion of the pilot portion is there into each other on a smooth curve; to provide a pilot portion for a center drill with vertical relief 55 by eliminated and should the pilot portion be a 2,403,861 3 4 come broken the clearance above the end cutting edges I9 will permit the operator to quickly re 2. A center drill having a body portion, a coun tersinking portion extending from said body por move the broken portion thereof. The clearance tion, a pilot portion extending from said coun is further useful in permitting free movement of the chips from the hole upwardly in the ?utes I6 in the body portion and in the countersinking and pilot portions. The arcuate countersinking portion of the hole readily receives the tapered end 25 of a center 26 and the circular line of engagement therebe 10 tersinking portion having an end cutting portion, and said pilot portion being joined on a smooth tween will be coined into a band of a width con curve. said portions having at least one ?ute therein, the section above said end cutting portion and below said countersinking portion being of less diameter than said end cutting portion to pro vide relief therefor, said countersinking portion forming to the amount of pressure applied be 3. A center drill having a body portion, a coun tween the center 26 and the work. The band pre tersinking portion extending from said body por vents the drifting of the center and work rela tion, a pilot portion extending from said coun tive to each other and is available after a hard 15 tersinking portion having an end cutting portion, ening operation to accurately center the work said portions having at least one ?ute therein, piece without the requirement of a separate the section above said end cutting portion and grinding operation which is employed to re-locate below said countersinking portion being of less the center after the hardening operation. diameter than said endvcutting portion to pro What is claimed is: 20 vide relief therefor, the form of said countersink v 1. A center drill having a body portion, a coun ing portion and said pilot portion being such that tersinking portion extending from said body por a plane in the longitudinal axis of said body por tion, a pilot portion extending from said coun tion intersects said portions on an arc of a circle tersinking portion having an end cutting por struck from a center located in said plane and tion, said portions having at least one ?ute there 25 spaced from the end cutting portion toward said in, the section above said end cutting portion and countersinking portion. below said countersinking portion being of less diameter than said end cutting portion to provide relief therefor.